Electrical insulating resin material, electrical insulating material, and electric wire and cable using the same

ABSTRACT

The present invention relates to a resin material for an electrical insulating material, an electrical insulating material and electric wire and cable using the same. A resin material for an electrical insulating material according to present invention is characterized in that the resin component thereof comprises an ethylene α-olefin copolymer (A) which satisfies specific conditions, such as a density of 0.92˜0.96 g/cm 3 , a melt flow rate (MFR) of 0.01˜200 g/10 minutes, a molecular weight distribution (Mw/Mn) of 1.5˜5.0, and possessing only one peak in terms of the number of peaks observed in an elution temperature-eluted amount curve as measured by the temperature raising elution fractionation (TREF) method, etc., wherein said resin component contains a unit derived from at least one type of monomer selected from among a carbonyl or carbonyl derivative group-containing monomer, a hydroxyl group-containing monomer, a nitro group-containing monomer, a nitrile group-containing monomer, an aromatic ring-containing monomer, and a compound or monomer containing two or more ethylenic linkages. This resin material for an electrical insulating material is suitable for use in an electrical insulating material for an electric wire and cable, as it exhibits excellent processability and electrical insulating properties without degradation of the mechanical strength, and even after cross-linking, exhibits superior electrical insulating properties.

TECHNICAL FIELD

The present invention relates to a resin material for an electricalinsulating material characterized in comprising an ethylene α-olefincopolymer possessing a superior processability and thermal resistance,in addition to an excellent mechanical strength and electricalinsulating properties; an electrical insulating material and electricwire and cable using the same. Specifically, the present inventionrelates to a resin material for an electrical insulating materialpossessing superior electrical insulating properties, such as volumeresistivity, space charge characteristics, dielectric breakdownstrength, and the like; a resin material for an electrical insulatingmaterial in which even after cross-linking, degradation of electricalinsulating properties, e.g., volume resistivity, space chargecharacteristics, dielectric breakdown strength, and the like does notoccur; and an electrical insulating material formed from theaforementioned resin material and cross-linked product, and electricwire and cable possessing an insulating layer using the same. Thisapplication is based on a patent application filed in Japan (JapanesePatent Application No. Hei 10-262105), the contents of which areincorporated herein by reference.

BACKGROUND ART

Conventionally, electrical insulating materials for electric wire andcables fundamentally require a high volume resistivity, and a highdielectric breakdown voltage, in addition to a low dielectric constantand dielectric dissipation factor, for which a polyethylene or the likeis generally used. In addition, as an electric power cable for use inmass transmission, such as a high-tension power cable and the like, acable which uses an insulating material to which oil has been filled(hereinafter referred to as “OF cable”) is routinely employed. However,this OF cable, despite possessing excellent electrical insulatingproperties, is disadvantageous in that oil often leaks out, which inturn necessitates a means for continuously supplying oil. In recentyears, a cross-linked polyethylene has been used which possesses anincreased thermal resistance and mechanical strength, and is obtained bymeans of cross-linking the polyolefin of a polyethylene or the like.

One of the problems associated with this high-tension power cable, whichuses a cross-linked polyethylene in its electrical insulating material,relates to the power loss that occurs during high-tension transmission.Hence, the reduction of this aforementioned power loss is highlydesirable. It is possible to reduce this power loss by means ofincreasing the electrical insulating performance of the electricalinsulating material, in particular by increasing the volume resistivity.

However, even by simply increasing the volume resistivity at either roomtemperature or constant temperature, this leads to other problems asdescribed below. For example, in a power cable, the electricalinsulating material around the inner conductor will reach 90° C. fromthe Joule heat of the electric current, however the electricalinsulating material around the outer conductor remains at atmospherictemperature. In the case of an electrical insulating material employinga conventional polyethylene in which extreme reductions in the volumeresistivity accompany temperature increase, an electrical field isconcentrated around the interface of the outer conductor and insulatingmember, which reduces the dielectric breakdown strength. Thisphenomenon, in particular, creates large problems with regard to dcelectric power cables. Accordingly, it is highly desirable to decreasethe temperature dependence of the volume resistivity of the electricalinsulating material.

With regard to a method for improving the temperature dependence of thevolume resistivity of the electrical insulating material, a method isproposed in which maleic anhydride is grafted to a low pressure processpolyethylene (e.g., Japanese Patent Application, First Publication No.Hei 2-10610 and the like). However, as an electrical insulatingmaterial, the electric power cables using this low pressure processpolyethylene shows an inferior flexibility when compared with conventionelectric power cables.

In this manner, as an electrical insulating material, electric powercables using a low density polyethylene to which maleic anhydride hasbeen grafted are proposed in Japanese Patent Application, FirstPublication No. Sho 63-150810, Japanese Patent Application, FirstPublication No. Sho 63-150811 and Japanese Patent Application, FirstPublication No. Hei 2-119012. However, the electrical insulatingmaterials used in these electric power cables are disadvantageous inthat the volume resistivity is reduced at high temperature.

In addition, in Japanese Patent Application, First Publication No. Hei5-266723, an electrical insulating material is obtained by means ofblending 100 parts by weight of a low density polyethylene, possessing adensity of 0.92 g/cm³, and 0.5 to 20 parts by weight of a linear lowdensity polyethylene, possessing a density of 0.91 to 0.94 g/cm³.However, the improvement of the temperature dependence of the volumeresistivity provided by means of this electrical insulating material isinadequate, since this electrical insulating material does notsufficiently improve the volume resistivity around the inner conductor.

In addition, a polyolefin such as polyethylene or the like, which isused as an electrical insulating material for electric wires and cables,may be employed after undergoing cross-linking in order to increaseproperties such as the thermal resistance and mechanical strength.

As methods for cross-linking a polyolefin such as polyethylene, anelectron beam cross-linking method and a chemical cross-linking method,which uses peroxides, are known. However, the electron beamcross-linking method requires large scale equipment, and possesses thedisadvantage of high cost. In addition, the chemical cross-linkingmethod, although economical, results in problems due to the existence ofan unreacted cross-linking agent, as this residue causes reduction ofthe volume resistivity, degradation of the space-charge characteristics,and generation of water-treeing.

As a method for improving the electrical insulating properties, e.g.,volume resistivity, space charge characteristics, water-treeingresistance, etc., a method in which a maleic anhydride-modifiedpolyolefin is added to polyethylene in order to introduce hydrophilicgroup is proposed in Japanese Patent Application, Second Publication No.Hei 5-15007. Furthermore, a trial is being conducted in an attempt toimprove the electrical insulating properties by means of introducing adouble bond into the polyolefin prior to cross-linking, and reducing theaddition amount of the cross-linking agent (Japanese Patent Application,First Publication No. Hei 4-11646). However, all of the aforementionedfail to produce both adequate electrical insulating properties, e.g.,volume resistivity and the like, and thermal resistance.

On the other hand, technology for improving the electrical insulatingproperties of electrical insulating material such as the volumeresistivity, dielectric breakdown strength and the like is beingproposed in which a carbonic acid compound and/or aromatic compound ismixed into a polyolefin. For example, various technologies are beingproposed for improving the impulse breakdown strength by means ofgrafting a styrene to a polyolefin (Japanese Patent Application, FirstPublication No. Hei. 2-165506); improving the impulse breakdown strengthby means of blending a polystyrene into polyethylene (Japanese PatentApplication, First Publication No. Sho. 63-301427); improving theelectrical insulating properties such as volume resistivity and the likemeans of blending a maleic acid-modified polyolefin into a polyethylene(Japanese Patent Application, First Publication No. Sho. 62-1000909);improving the dielectric breakdown characteristics by means of blendingan aromatic carboxylic acid into a polyolefin (Japanese PatentApplication, First Publication No. Sho. 60-23904); and the like.

However, all of the aforementioned technologies are not able to achievesufficient improvement of both the volume resistivity and dielectricbreakdown strength. In addition, the electrical insulating propertieseven after cross-linking are inadequate.

On the other hand, Japanese Patent Application, First Publication No.Hei 9-17235 discloses electrical insulating material comprising a highmechanical strength and low electrical activation energy by means ofemploying a specific ethylene copolymer of a narrow compositiondistribution.

However, the composition distribution of the aforementioned ethylenecopolymer is extremely narrow, while the change in viscosity andstrength with respect to temperature is extreme, which in turn leads tonarrowing of the appropriate range of conditions such as the temperatureat the time of polymer processing, extrusion conditions, and the like,and results in poor processability.

In addition, an electrical insulating material employing an ethylenepolymer manufactured by means of using a metallocene catalyst, andelectric wire and cable using the same are disclosed in Japanese PatentApplication, First Publication No. Hei 6-509905, Japanese PatentApplication, First Publication No. Hei 8-111121, and Japanese PatentApplication, First Publication No. Hei 8-222026. However, although thesedisclosures achieve an improvement in the treeing resistance, theappropriate range of conditions such as the temperature at the time ofpolymer processing, extrusion conditions, and the like are narrow, whichin turn results in poor processability.

As a means for improving the processability of the ethylene polymermanufactured by means of using a metallocene catalyst, methods are knownin which components of differing molecular weights are blended together,or the ethylene polymer is polymerized in multiple stages. However, evenwhen using these types of means for improving the processability, it isstill difficult to always achieve a sufficient improvement in theprocessability of the ethylene polymer manufactured by means of using ametallocene catalyst.

Furthermore, a method for blending an ethylene polymer manufactured bymeans of using a metallocene catalyst, and ethylene polymer of differentmolecular weight manufactured by means of using a Ziegler catalyst or aPhillips catalyst, are disclosed in, for example, Japanese PatentApplication, First Publication No. Hei 9-505090. However, thedispersability of the aforementioned is insufficient, resulting indisadvantages such as melt fractures, and reduction of the mechanicalstrength.

In order to solve the aforementioned problems, Japanese PatentApplication, First Publication No. Hei 9-302160 discloses a resincomposition for an electrical insulating material comprising a resincomponent of an ethylene homopolymer or an ethylene copolymer satisfyingspecific parameters, such as a density of 0.86 to 0.96 g/cm³, MFR of0.01 to 200 g/10 minutes, molecular weight distribution (Mw/Mn) of 1.5to 5.0, a composition distribution parameter of no greater than 2.00,and an electrical activation energy of no greater than 0.4 eV, whichcontains a monomer unit selected from among a carbonyl or carbonylderivative group-containing monomer, hydroxyl group-containing monomer,nitro group-containing monomer, nitrile group-containing monomer,aromatic ring-containing monomer and a compound or monomer containingtwo or more ethylenic linkages. However, a resin composition for anelectrical insulating material, which further improves properties suchas thermal resistance and the like, is required.

The present invention provides a resin material for an electricalinsulating material possessing a superior processability and thermalresistance, in addition to superior electrical insulating properties,such as volume resistivity, space charge characteristics, dielectricbreakdown strength, water-treeing resistance, and the like, in which areduction in the mechanical strength does not occur; or a resin materialfor an electrical insulating material which is rich incross-linkability, and even after cross-linking, exhibits superiorvolume resistivity, space-charge characteristics, dielectric breakdownstrength, water-treeing resistance and the like; and an electricalinsulating material formed from the aforementioned resin material and/orcross-linked product, and electric wire and cable possessing aninsulating layer using the same.

DISCLOSURE OF INVENTION

The resin material for an electrical insulating material according tothe present invention is characterized in that the resin componentthereof comprises an ethylene α-olefin copolymer (A), obtained by meansof copolymerizing ethylene and C₄₋₁₂ α-olefin, said ethylene α-olefincopolymer (A) satisfying specific parameters (i) to (v):

(i) a density of 0.92 to 0.96 g/cm³,

(ii) a melt flow rate (MFR) of 0.01 to 200 g/10 minutes,

(iii) a molecular weight distribution (Mw/Mn) of 1.5 to 5.0,

(iv) possessing only one peak in terms of the number of peaks observedin an elution temperature-eluted amount curve as measured by thecontinuous temperature raising elution fractionation (TREF) method, andfrom the integrated elution curve obtained by said elutiontemperature-eluted amount curve, the difference T₇₅−T₂₅ in thetemperature and said density d respectively follow the relationshipsshown by formula a and formula b, wherein T₂₅ is the temperature where25% of the total elution is obtained, and T₇₅ is the temperature where75% of the total elution is obtained; and (v) possessing one or twomelting point peaks, and among these the highest melting point T_(m1)and said density d follow the relationship described by formula c;

wherein said resin component contains a unit (B) derived from at leastone type of monomer selected from among a carbonyl or carbonylderivative group-containing monomer (M1), a hydroxyl group-containingmonomer (M2), a nitro group-containing monomer (M3), a nitrilegroup-containing monomer (M4), an aromatic ring-containing monomer (M5)and a compound or monomer containing two or more ethylenic linkages(M6); and when said unit (B) is derived from at least one type ofmonomer selected from M1 to M5, the concentration of said unit (B)ranges from 5×10⁻⁷ to 5×10⁻³ mol per one gram of said resin component,and when said unit (B) is derived from M6, the number of ethyleniclinkages per 1000 carbon atoms of said resin component is at least 0.8.

if d<0.950 g/cm³, then  (Formula a)

T ₇₅ −T ₂₅≧−300×d+285

if d≧0.950 g/cm³, then

T ₇₅ −T ₂₅≧0

 T ₇₅ −T ₂₅<−670×d+644  (Formula b)

T _(m1)≧150d−17  (Formula c)

This resin material for an electrical insulating materials displayssuperior processability and thermal resistance, in addition to superiorelectrical insulating properties, such as volume resistivity, spacecharge characteristics, dielectric breakdown strength, water-treeingresistance, and the like, in which a reduction in the mechanicalstrength does not occur. In addition, the resin material for anelectrical insulating is rich in cross-linkability, and even aftercross-linking, exhibits superior volume resistivity, space chargecharacteristics, dielectric breakdown strength, water-treeing resistanceand the like.

In addition, the aforementioned ethylene α-olefin copolymer (A) alsosatisfies specific conditions (i) to (vii):

(i) a density of 0.92 to 0.96 g/cm³,

(ii) a melt flow rate (MFR) of 0.01 to 200 g/10 minutes,

(iii) a molecular weight distribution (Mw/Mn) of 1.5 to 3.5,

(iv) possessing only one peak in terms of the number of peaks observedin an elution temperature-eluted amount curve as measured by thecontinuous temperature raising elution fractionation (TREF) method, andfrom the integrated elution curve obtained by said elutiontemperature-eluted amount curve, the difference T₇₅−T₂₅ in thetemperature and said density d respectively follow the relationshipsshown by formula a and formula b, wherein T₂₅ is the temperature where25% of the total elution is obtained, and T₇₅, is the temperature where75% of the total elution is obtained;

(v) possessing one or two melting point peaks, and among these thehighest melting point T_(m1) and said density d follow the relationshipdescribed by formula c;

(vi) an electrical activation energy of no greater than 0.4 eV; and

(vii) the melt tension (MT) and melt flow rate (MFR) follow therelationship shown by formula d.

if d<0.950 g/cm³, then  (Formula a)

T₇₅ −T ₂₅≧−300×d+285

if d≧0.950 g/cm³, then

T ₇₅ −T ₂₅≧0

T ₇₅ −T ₂₅≧−670×d+644  (Formula b)

T _(m1)≧150×d−17  (Formula c)

log MT≦−0.572×log MFR+0.3  (Formula d)

The resin material for an electrical insulating material comprising thisethylene α-olefin copolymer (A) displays a superior processability andthermal resistance, in addition to superior electrical insulatingproperties, such as volume resistivity, space charge characteristics,dielectric breakdown strength, water-treeing resistance, and the like,in which a reduction in the mechanical strength does not occur. Inaddition, the resin material for an electrical insulating material isrich in cross-linkability, and even after cross-linking, exhibitssuperior volume resistivity, space charge characteristics, dielectricbreakdown voltage, water-treeing resistance and the like.

In addition, said ethylene α-olefin copolymer (A) is preferably obtainedby means of copolymerizing ethylene and C₄₋₁₂ α-olefin under thepresence of a catalyst comprising a cyclic organic compound containingat least a conjugated double bond, and a compound containing transitionmetal from group IV of the Periodic Table. The resin material for anelectrical insulating material comprising this ethylene α-olefincopolymer (A) displays a more superior processability, thermalresistance, mechanical strength, and electrical insulating properties.

In addition, the halogen concentration within said ethylene α-olefincopolymer (A) is preferably no greater than 10 ppm. The resin materialfor an electrical insulating material comprising this ethylene α-olefincopolymer (A) does not require the addition of additives such as halogenacceptor or the like, and thus maintains superior electrical insulatingproperties.

In addition, said resin component may also comprise said ethyleneα-olefin copolymer (A), and another polyolefin (A′).

In addition, said other polyolefin (A′) is preferably at least onecompound selected from among a polyethylene obtained by means of a highpressure radical polymerization, a high density polyethylene, a mediumdensity polyethylene, and a linear low density polyethylene. The resinmaterial for an electrical insulating comprising this other polyolefin(A′) exhibits superior extrusion molding characteristics.

In addition, said carbonyl or carbonyl derivative group-containingmonomer (M1) to be introduced into said resin component is preferably atleast one compound selected from among maleic anhydride and(meth)acrylic acid. The resin material for an electrical insulatingmaterial introducing this monomer unit results in a large improvement inthe volume resistivity.

In addition, a maleic anhydride-modified ethylene α-olefin copolymer (A)is preferably used at the time said carbonyl or carbonyl derivativegroup-containing monomer (M1) is introduced into said resin component.The resin material for an electrical insulating material comprising thiscopolymer results in a particularly large improvement in the volumeresistivity.

In addition, a polystyrene, an ethylene-styrene random copolymer, or anethylene copolymer (A), which has been modified by means of grafting anaromatic ring-containing monomer, is preferably used at the time saidaromatic ring-containing monomer (M5) is introduced into said resincomponent. The resin material for an electrical insulating materialcomprising this copolymer results in a large improvement in thedielectric breakdown strength.

In addition, at least one compound selected from among an liquidpolybutadiene, a maleic anhydride-modified liquid polybutadiene, anethylene-aryl(meth)acrylate copolymer, and anethylene-vinyl(meth)acrylate copolymer is preferably used at the timesaid compound or monomer containing two or more ethylenic linkages (M6)is introduced into said resin component. The resin material for anelectrical insulating material comprising these polymer or copolymerdisplays superior electrical insulating properties after cross-linkingand an excellent cross-linking efficiency.

In addition, said resin component preferably contains said compound ormonomer containing two or more ethylenic linkages (M6) and said carbonylor carbonyl derivative group-containing monomer (M1). The resin materialfor an electrical insulating material introducing these monomers shows asuperior cross-linking efficiency and volume resistivity.

In addition, a maleic anhydride-modified liquid polybutadiene and amaleic anhydride-modified ethylene cc-olefin copolymer (A) arepreferably used at the time said carbonyl or carbonyl derivativegroup-containing monomer (M1) and said compound or monomer containingtwo or more ethylenic linkages (M6) are introduced into said resincomponent. The resin material for an electrical insulating materialcomprising these copolymers results in large improvements of theelectrical insulating properties after cross-linking, cross-linkingefficiency, and volume resistivity.

In addition, said resin component preferably contains said compound ormonomer containing two or more ethylenic linkages (M6) and said aromaticring-containing monomer (M5). The resin material for an electricalinsulating material introducing these monomers displays a superiorcross-linking efficiency, volume resistivity, and dielectric breakdownstrength.

In addition, a maleic anhydride-modified liquid polybutadiene and anethylene-styrene random copolymer are preferably used at the time saidcompound or monomer containing two or more ethylenic linkages (M6) andsaid aromatic ring-containing monomer (M5) are introduced into saidresin component. The resin material for an electrical insulatingcomprising these copolymers results in large improvements of theelectrical insulating properties after cross-linking, cross-linkingefficiency, volume resistivity, and dielectric breakdown strength.

In addition, said resin component preferably contains said carbonyl orcarbonyl derivative group-containing monomer (M1) and said aromaticring-containing monomer (M5). The resin material for an electricalinsulating material introducing these monomers displays a superiorvolume resistivity and dielectric breakdown strength.

In addition, a maleic anhydride-modified ethylene α-olefin copolymer (A)and an ethylene-styrene random copolymer are preferably used at the timesaid carbonyl or carbonyl derivative group-containing monomer (M1) andsaid aromatic ring-containing monomer (M5) are introduced into saidresin component. The resin material for an electrical insulatingmaterial comprising these copolymers results in large improvements ofthe volume resistivity, and dielectric breakdown strength.

In addition, said resin component preferably contains said carbonyl orcarbonyl derivative group-containing monomer (M1), said compound ormonomer containing two or more ethylenic linkages (M6), and saidaromatic ring-containing monomer (M5). The resin material for anelectrical insulating material introducing these monomers displays asuperior cross-linking efficiency, volume resistivity, and dielectricbreakdown strength.

In addition, a maleic anhydride-modified liquid polybutadiene, a maleicanhydride-modified ethylene α-olefin copolymer (A) and anethylene-styrene random copolymer are preferably used at the time saidcarbonyl or carbonyl derivative group-containing monomer (M1), saidcompound or monomer containing two or more ethylenic linkages (M6), andsaid aromatic ring-containing monomer (M5) are introduced into saidresin component. The resin material for an electrical insulatingmaterial comprising these copolymers results in large improvements ofthe electrical insulating properties after cross-linking, cross-linkingefficiency, volume resistivity, and dielectric breakdown strength.

In addition, the electrical insulating material according to the presentinvention is characterized in using the aforementioned resin materialfor an electrical insulating material. This electrical insulatingmaterial displays a superior processability, mechanical strength, andelectrical insulating properties.

In addition, the electrical insulating material according to the presentinvention preferably comprises a maleic anhydride-modified ethyleneα-olefin copolymer (A).

In addition, the electrical insulating material according to the presentinvention preferably comprises a maleic anhydride-modified ethyleneα-olefin copolymer (A) and an ethylene-styrene random copolymer.

In addition, the electrical insulating material according to the presentinvention is characterized in that a resin material for an electricalinsulating described in the aforementioned is cross-linked. Thiselectrical insulating material displays an even more superior mechanicalstrength.

In addition, the electrical insulating material according to the presentinvention preferably comprises a cross-linked resin material for anelectrical insulating material comprising a maleic anhydride-modifiedliquid polybutadiene, and a maleic anhydride-modified ethylene α-olefincopolymer (A).

In addition, the electrical insulating material according to the presentinvention preferably comprises a cross-linked resin material for anelectrical insulating material comprising a maleic anhydride-modifiedliquid polybutadiene, and an ethylene-styrene random copolymer.

In addition, the electrical insulating material according to the presentinvention preferably comprises a cross-linked resin material for anelectrical insulating material comprising a maleic anhydride-modifiedliquid polybutadiene, maleic anhydride-modified ethylene α-olefincopolymer (A) and an ethylene-styrene random copolymer.

In addition, the electric wire and cable according to the presentinvention is characterized in using cross-linked or non-cross-linkedelectrical insulating material described above as an insulating layer.This electric wire and cable display a superior mechanical strength andelectrical insulating properties.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a graph showing an example of a TREF curve of an ethyleneα-olefin copolymer (A) in the present invention.

FIG. 2 is a diagram showing an electrode system for measuring the volumeresistivity: FIG. 2A shows a top view; and FIG. 2B shows a sidecross-section view.

FIG. 3 is a cross-sectional diagram showing a measuring apparatus forthe breakdown voltage test.

FIG. 4 is a diagram showing a side cross-sectional view of an apparatusfor measuring the water-treeing.

FIG. 5 is a cross-sectional view showing an example of an electric powercable of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

In the following, the present invention is described in detail.

The ethylene α-olefin copolymer (A) of the present invention(hereinafter referred to as “ethylene copolymer (A)”) is obtained bymeans of copolymerizing ethylene and C₄₋₁₂ α-olefin, and satisfiesspecific condition (i) to (v):

(i) a density of 0.92 to 0.96 g/cm³,

(ii) a melt flow rate (MFR) of 0.01 to 200 g/10 minutes,

(iii) a molecular weight distribution (Mw/Mn) of 1.5 to 5.0,

(iv) possessing only one peak in terms of the number of peaks observedin an elution temperature-eluted amount curve as measured by thecontinuous temperature raising elution fractionation (TREF) method, andfrom the integrated elution curve obtained by said elutiontemperature-eluted amount curve, the difference T₇₅−T₂₅ in thetemperature and said density d respectively follow the relationshipsshown by formula a and formula b, wherein T₂₅ is the temperature where25% of the total elution is obtained, and T₇₅ is the temperature where75% of the total elution is obtained; and

(v) possessing one or two melting point peaks, and among these thehighest melting point T_(m1) and said density d follow the relationshipdescribed by formula c;

if d<0.950 g/cm³, then  (Formula a)

T ₇₅ −T ₂₅≧−300×d+285

if d ≧0.950 g/cm³, then

T ₇₅ −T ₂₅≦0

T ₇₅ −T ₂₅≧−670×d+644  (Formula b)

T _(m1)≧150×d−17  (Formula c)

The α-olefin of the ethylene copolymer (A) according to the presentinvention comprises from 4 to 12 carbon atoms, and preferably from 5 to10 carbon atoms, including 1-pentene, 4-methyl-1-pentene, 1-hexene,1-octene, 1-decene, 1-dodecene, and the like. In addition, the totalconcentration of the α-olefin is preferably no greater than 30 mol %,and more preferably 3 to 20 mol %.

The density of the ethylene copolymer (A) according to the presentinvention is within the range of 0.92 to 0.96 g/cm³ (i), preferably0.925 to 0.94 g/cm³, and more preferably 0.925 to 0.935 g/cm³. A densityof less than 0.92 g/cm³ leads to a product of inferior rigidity andthermal resistance, while a density exceeding 0.96 g/cm³ produces aproduct that is excessively hard, leading to a reduction in mechanicalstrength, e.g., impact strength.

The melt flow rate (hereinafter referred to as “MFR”) of the ethylenecopolymer (A) according to the present invention is 0.01 to 200 g/10minutes (ii), preferably 0.05 to 50 g/10 minutes, and more preferably0.1 to 40 g/10 minutes. An MFR less than 0.01 g/10 minutes leads to apoor processability, while an MFR exceeding 200 g/10 minutes leads to alow mechanical strength.

The molecular weight distribution (Mw/Mn) of the ethylene copolymer (A)according to the present invention is within the range of 1.5 to 5.0(iii), and preferably within the range of 1.5 to 3.5. A Mw/Mn of lessthan 1.5 leads to a poor processability, while a Mw/Mn exceeding 5.0leads to a low mechanical strength, e.g., impact strength.

In general, the molecular weight distribution (Mw/Mn) of the ethylenecopolymer (A) can be obtained by means of obtaining the weight averagemolecular weight (Mw) and number average molecular weight (Mn) by meansof gel permeation chromatography (GPC), and then calculating the ratio(Mw/Mn) therefrom.

The ethylene copolymer (A) according to the present invention, as shownin FIG. 1, possesses only one peak in terms of the number of peaksobserved in an elution temperature-eluted amount curve as measured bythe continuous temperature raising elution fractionation (TREF) method,and from the integrated elution curve observed by said elutiontemperature-eluted amount curve, the difference T₇₅−T₂₅ in thetemperature and said density d respectively follow the relationshipsshown by formula a and formula b (iv), wherein T₂₅ is the temperaturewhere 25% of the total elution is obtained, and T₇₅ is the temperaturewhere 75% of the total elution is obtained.

if d<0.950 g/cm³, then  (Formula a)

T ₇₅ −T ₂₅≧−300×d+285

ifd≧0.950 g/cm³, then

 T ₇₅ −Th ₂₅24 0

T ₇₅ −T ₂₅≦−670×d+644  (Formula b)

In the case when T₇₅−T₂₅ and density d do not satisfy the aforementionedrelationship shown by formula a, an inferior thermal resistance results;and when T₇₅−T₂₅ and density d do not satisfy the aforementionedrelationship shown by formula b, an inferior processability results atlow temperatures.

The method for measuring the TREF in the present invention is describedin the following. The sample is added to orthodichlorobenzene (ODCB)which has been treated with an antioxidant (e.g., butylhydroxytoluene)until the concentration of the sample reaches 0.05% by weight, whileheating at 135° C. to dissolve the sample. Subsequently, 5 ml of thesample solution is introduced into a column packed with glass beads, andcooled to 25° C. at a cooling rate of 0.1° C./minute to deposit thesample onto the surface of the glass beads. Thereafter, the sample issuccessively eluted while pouring the ODCB through the column at a fixedflow amount and increasing the column temperature at a fixed rate of 50°C/hr. At this time, the concentration of the sample to be eluted intothe solvent is continuously detected by means of measuring theabsorption at a wave number of 2925 cm⁻¹ of the asymmetric stretchingvibration of the methylene by means of an infrared detector. From thisvalue, the quantitative analysis concentration of the ethylene α-olefincopolymer is performed, and the relationship between the elutiontemperature and elution rate is obtained. According to the TREFanalysis, it is possible to continuously analyze the change of elutionrate, and thus it is also possible to detect relatively fine peaks whichwere undetectable according to fraction methods.

In addition, the ethylene copolymer (A) according to the presentinvention possesses one or two melting point peaks, and among these thehighest melting point T_(m1) and said density d follow the relationshipdescribed by formula c (v).

 T _(ml)≧150×d−17   (Formula c)

If the melting point T_(m1) and density d do not satisfy therelationship expressed in the aforementioned (formula c), an inferiorthermal resistance results. The ethylene polymer manufactured by meansof using a conventional metallocene catalyst disclosed in JapanesePatent Application, First Publication No. Hei 6-509905, and the like,does not satisfy this requisite condition (v).

The electrical activation energy of the ethylene copolymer (A) accordingto the present invention is preferably 0.4 eV or less (vi), morepreferably 0.3 eV or less, and even more preferably 0.25 eV or less. Ifthe electrical activation energy exceeds 0.4 eV, the quantity andmobility of charged carriers such as ion and electron dramaticallyincreases with increases in the temperature, resulting in a degradationof the thermal and chemical stability thereof.

The aforementioned value is an extremely small value, however, whencompared with conventional polyethylene materials. It is thus consideredthat the ethylene copolymer (A) according to the present inventionpossess a specific structure such that quantity and mobility of chargedcarriers contained therein have little influence on the temperature.

Here, the activation energy is one of the constants incorporated intothe Arrhenius' equation for expressing the change of rate constant withtemperature during the process of the transport phenomenon. Thisactivation energy correlates with the difference in energy between thetransition state and original system in the process toward the producedsystem from the original system via the transition state. In particular,the electrical activation energy is used in the Arrhenius' equation forexpressing the temperature dependence of the electric current. A smallelectrical activation energy reflects a small temperature dependence ofthe electric current.

The electrical activation energy (U) according to the present inventioncan be determined from the following equation (Arrhenius' equation).

 I∝exp (−U/kT)

(I: electric current, k: Boltzmann's constant, T: absolute temperature)

According to the aforementioned equation, the electrical activationenergy can be obtained by means of entering the electric current valuesat room temperature (20° C.) and at 90° C.

Furthermore, the ethylene copolymer (A) according to the presentinvention preferably satisfies the condition (vii).

(vii) the melt tension (MT) and melt flow rate (MFR) follow therelationship shown by formula d.

log MT≦−0.572×log MFR+0.3  (Formula d)

A melt tension (MT) and melt flow rate (MFR) satisfy the relationship byformula d, an excellent processability results.

The ethylene copolymer (A) according to the present invention has amolecular weight distribution that is broader than the ethylenecopolymer obtained under the presence of a typical, conventionalmetallocene catalyst, i.e., at least one type of catalyst-containingligand possessing a cyclopentadienyl structure and compound containingtransition metal from group IV of the Periodic Table. In addition, theethylene copolymer (A) according to the present invention possessessuperior low temperature forming properties compared with a low densityethylene α-olefin copolymer obtained using a Ziegler-type catalyst, andhence clearly differs from the aforementioned ethylene copolymers.

The ethylene copolymer (A) according to the present invention is notparticularly limited with respect to the catalyst and manufacturingmethod used, as long as it satisfies the aforementioned specificconditions; however, the ethylene copolymer (A) according to the presentinvention preferably is obtained by means of copolymerizing ethylene andC₄₋₁₂ α-olefin under the presence of a catalyst comprising a cyclicorganic compound containing at least a conjugated double bond, and acompound containing transition metal from group IV of the PeriodicTable. By means of using this type of catalyst, the aforementionedspecific conditions can be easily satisfied.

When the ethylene copolymer (A) according to the present invention isobtained by means of polymerization under the presence of a catalystobtained by means of mixing compounds which do not contain a halogen,selected from among the following compounds (a1)˜(a4), then the additionof a halogen acceptor becomes unnecessary, resulting in no degradationof the electrical properties, which is particularly preferred. Forexample, in this manner, it is possible to obtain an ethylene copolymerwhich satisfies the condition of (vi) an electrical activation energy ofno greater than 0.4 eV.

(a1) a compound represented by the general formula of Me¹R¹ _(p)R² _(q)(OR³)_(r)X¹ _(4-p-q-r)

(wherein, Me¹ represents zirconium, titanium, or hafnium; R¹ and R³ eachrespectively represents a C₁₋₂₄ hydrocarbon group; R² represents a2,4-pentadionate ligand or derivative thereof, a benzoyl methanateligand, a benzoyl acetanate ligand or derivative thereof; X¹ representsa halogen atom; and p, q and r each represent integers satisfying theranges of 0≦p≦4, 0 q≦4, and 0≦r≦4, such that 0≦p+q+r4≦, respectively).

(a2) a compound represented by the general formula of Me²R⁴ _(m)(OR⁵)_(n)X² _(z-m-n)

(wherein, Me² represents an element from groups I˜III of the PeriodicTable; R⁴ and R⁵ each respectively represents a C₁₋₂₄ hydrocarbon group;X² represents a halogen atom or a hydrogen atom (with the proviso thatwhen X² represents a hydrogen atom, Me² is limited to an element fromgroup III of the Periodic Table); z represents the valence of Me²; and mand n each represent integers satisfying the ranges of 0≦m≦z, and 0≦n≦z,such that 0≧m+n≧z, respectively).

(a3) an cyclic organic compound having a conjugated double bond

(a4) modified organoaluminumoxy compound containing an Al—O—Al bondand/or boron compound.

In the following, the catalytic component will be described in greaterdetail.

In the formula of the compound expressed by the general formula Me¹R¹_(p)R² _(q)(OR³)_(r)X¹ _(p-r-q) of the aforementioned catalyst component(a1), Me¹ represents zirconium, titanium, or hafnium. The kind of such atransition metal is not particularly limited, and may also be used incombinations of two or more. Among the aforementioned, zirconium, whichis able provide a copolymer superior in weather resistance, isparticularly preferred. R¹ and R³ each represent a C₁₋₂₄ hydrocarbongroup, preferably C₁₋₁₂, and more preferably C₁₋₁₈ hydrocarbon group.Concrete examples may include an alkyl group such as a methyl group,ethyl group, propyl group, isopropyl group, butyl group, and the like;an alkenyl group such as a vinyl group, allyl group, and the like; andaryl group such as a phenyl group, tolyl group, xylyl group, mesitylgroup, indenyl group, naphthyl group, and the like; and an aralkyl groupsuch as a benzyl group, trityl group, phenethyl group, styryl group,benzhydryl group, phenylbutyl group, neophyl group, and the like. Theseaforementioned compounds may also be branched. R² represents a2,4-pentanedionate ligand or derivative thereof, a benzoyl methanateligand, or a benzoyl acetonate ligand or derivative thereof; X¹represents a halogen atom such a fluorine, iodine, chlorine, bromine,and the like; and p, q and r each represent integers satisfying theranges of O≦p≦4, 0≦q≦4 and 0≦r≦4, such that 0≦p+q+r≦4, respectively.

Examples of the compounds expressed by the general formula of theaforementioned catalyst component (aB) may include tetramethylzirconium, tetraethyl zirconium, tetrabenzyl zirconium, tetrapropoxyzirconium, tripropoxy monochloro zirconium, tetraethoxy zirconium,tetrabutoxy zirconium, tetrabutoxy titanium, tetrabutoxy hafnium, andthe like. Among these, Zr(OR)₄ compounds such as tetrapropoxy zirconium,tetrabutoxy zirconium, and the like, are particularly preferred, and amixture of two or more types may also be used. In addition, concreteexamples of the complex containing the aforementioned 2,4-pentanedionateligand or derivative thereof, benzoyl methanate ligand, and benzoylacetonate ligand or derivative thereof may include zirconiumtetra(2,4-pentanedionate), zirconium tri(2,4-pentanedionate) chloride,zirconium di(2,4-pentanedionate) dichloride, zirconium(2,4-pentanedionate) trichloride, zirconium di(2,4-pentanedionate)diethoxide, zirconium di(2,4-pentanedionate) di-n-propoxide, zirconiumdi(2,4-pentanedionate) di-n-butoxide, zirconium di(2,4-pentanedionate)dibenzyl, zirconium di(2,4-pentanedionate) dineophyl, zirconiumtetra(dibenzoyl methanate), zirconium di(dibenzoyl methanate)diethoxide, zirconium di(dibenzoyl methanate) di-n-propoxide, zirconiumdi(dibenzoyl methanate) di-n-butoxide, zirconium di(benzoyl acetonate)diethoxide, zirconium di(benzoyl acetonate) di-n-propoxide, zirconiumdi(benzoyl acetonate) di-n-butoxide, and the like.

In the formula of the compound expressed by the general formula Me²R⁴_(m)(OR⁵)_(n)X² _(z-m-n) of the aforementioned catalyst component (a2),Me² represents an element from groups I˜III of the Periodic Table;examples of which include lithium, sodium, potassium, magnesium,calcium, zinc, boron, aluminum, and the like. R⁴ and R⁵ eachrespectively represents a C₁₋₂₄ hydrocarbon group, preferably C₁₋₁₂, andmore preferably C₁₋₈ hydrocarbon group. Concrete examples may include analkyl group such as a methyl group, ethyl group, propyl group, isopropylgroup, butyl group, and the like; an alkenyl group such as a vinylgroup, allyl group, and the like; aryl group such as phenyl group, tolylgroup, xylyl group, mesityl group, indenyl group, naphthyl group, andthe like; and an aralkyl group such as a benzyl group, trityl group,phenethyl group, styryl group, benzhydryl group, phenylbutyl group,neophyl group, and the like. These aforementioned compounds may also bebranched. X² represents a hydrogen atom or a halogen atom such asfluorine, iodine, chlorine, bromine and the like. When X² represents ahydrogen atom, Me² is limited to an element from group III of thePeriodic Table such as boron, aluminum. In addition, z represents thevalence of Me²; and m and n each represent integers satisfying theranges of 0≦m≦z, and 0≦n≦z, such that 0≦m+n≦z, respectively.

Examples of the compound expressed by the general formula of theaforementioned catalyst component (a2) may include organic lithiumcompounds such as methyl lithium, ethyl lithium, and the like; organicmagnesium compounds such as dimethyl magnesium, diethyl magnesium,methyl magnesium chloride, ethyl magnesium chloride, and the like;organic zinc compound such as dimethyl zinc, diethyl zinc, and the like;organic boron compounds such as trimethyl boron, triethyl boron, and thelike; and derivatives of organoaluminum compounds and the like such astrimethyl aluminum, triethyl aluminum, tripropyl aluminum, triisobutylaluminum, trihexyl aluminum, tridecyl aluminum, diethyl aluminumchloride, ethyl aluminum dichloride, ethyl aluminum sesquichloride,diethyl aluminum ethoxide, diethyl aluminum hydride, and the like.

The cyclic organic compound having a conjugated double bond of theaforementioned catalyst component (a3) contains a C₄₋₂₄, preferablyC₄₋₁₂ cyclic hydrocarbon compound comprising at least one ringcontaining two or more conjugated double bonds, preferably two to fourconjugated double bonds, and more preferably two or three conjugateddouble bonds; a cyclic hydrocarbon compound, wherein a portion of theaforementioned cyclic hydrocarbon compound is substituted with one tosix residual hydrocarbon groups, (typically, with C₁₋₁₂ alkyl group oraralkyl group); an organic silicon compound containing C₄₋₂₄, preferablyC₄₋₁₂ cyclic hydrocarbon group, and comprising two or more conjugateddouble bonds, preferably two to four conjugated double bonds, and morepreferably two or three conjugated double bonds; and an organic siliconcompound, wherein a portion of the aforementioned cyclic hydrocarbon issubstituted with one to six hydrocarbon residues or alkali metal salt(such as sodium or lithium salt). In particular, cyclic organiccompounds having cyclopentadiene structure anywhere in its molecule arepreferred.

Preferred examples of the aforementioned compound may includecyclopentadiene, indene, azulene, as well as alkyl, aryl, aralkyl,alkoxy, or aryloxy derivatives thereof. In addition, compounds in whichthese aforementioned compounds are bonded (cross-linked) via alkylenegroup (normally C₂₋₈, preferably C₂₋₃ alkylene group), may be suitablyused.

The organic silicon compound having a cyclic hydrocarbon group may beexpressed by the following general formula.

A_(L)SiR_(4-L)

Here, A represents the aforementioned cyclic hydrocarbon group such as acyclopentadienyl group, substituted cyclopentadienyl group, indenylgroup, and substituted indenyl group; R represents a hydrogen atom orC₁₋₂₄, preferably C₁₋₁₂ hydrocarbon residue such as alkyl group such asa methyl group, ethyl group, propyl group, isopropyl group, butyl group,and the like; an alkoxy group such as a methoxy group, ethoxy group,propoxy group, butoxy group, and the like; an aryl group such as aphenyl group, and the like; an aryloxy group such as a phenoxy group,and the like; or an aralkyl group such as a benzyl group, and the like;and L satisfies 1≦L<4, preferably 1≦L<3.

Concrete examples of the cyclic organic hydrocarbon compound of theaforementioned component (a3) include C₅₋₂₄ cyclopolyene or substitutedcyclopolyene such as cyclopentadiene, methylcyclopentadiene,ethylcyclopentadiene, 1,3-dimethylcyclopentadiene, indene,4-methyl-1-indene, 4,7-dimethylindene, cycloheptatriene,methylcycloheptatriene, cyclooctatetraene, azulene, fluorene, and methylfluorene; monocyclopentadienyl silane; biscyclopentadienyl silane;tricyclopentadienyl silane; monoindenyl silane; bisindenyl silane;trisindenyl silane; and the like.

The modified organoaluminumoxy compound containing an Al—O—Al bond ofthe catalyst component (a4) is normally a modified organoaluminumoxycompound referred to as “aluminoxane”, which can be obtained by means ofreacting an alkyl aluminum compound with water, and contains normally 1to 100 Al—O—Al bonds, preferably 1 to 50 Al—O—Al bonds, in a molecule.In addition, the modified organoaluminumoxy compound containing anAl—O—Al bond may comprise either a linear or cyclic structure.

The reaction of the organic aluminum compound with water is normallyperformed in an inactive hydrocarbon, preferred examples of whichinclude aliphatic, alicyclic, and aromatic hydrocarbons such as pentane,hexane, heptane, cyclohexane, benzene, toluene, xylene, and the like.

The reaction ratio of the water and organic aluminum compound (water toAl ratio in mol) is normally 0.25/1˜1.2/1, and preferably 0.5/1˜1/1.

Examples of the boron compound may include triethylaluminumtetra(pentafluorophenyl) borate, triethylammoniumtetra(pentafluorophenyl) borate, dimethylaniliniumtetra(pentafluorophenyl) borate, dimethylaniliniumtetra(pentafluorophenyl) borate, butylammoniumtetra(pentafluorophenyl)borate, N,N-dimethylaniliniumtetra(pentafluorophenyl) borate, N,N-dimethylaniliniumtetra(3,5-difluorophenyl) borate, and the like.

The aforementioned catalyst components (a1) to (a4) may be mixed intocontact and used. These components are preferably supported on aninorganic carrier and/or particulate polymer carrier (a5), and are used.

Examples of the aforementioned inorganic carrier and/or particulatepolymer carrier (a5) may include carbon material, metal, metallic oxide,metallic chloride, metallic carbonate, and mixtures thereof,thermoplastic resins, or thermosetting resins, and the like. Preferredexamples of the metal that can be used as inorganic carrier includesiron, aluminum, nickel, and the like.

Concrete examples of the aforementioned may include SiO₂, Al₂O₃, MgO,ZrO₂, TiO₂, B₂O₃, CaO, ZnO, BaO, ThO₂, and the like, and mixturesthereof, including SiO₂—Al₂O₃, SiO₂—V₂O₅, SiO₂—TiO₂, SiO₂—V₂O₅,SiO₂—MgO, SiO₂—Cr₂O₃, and the like. Among the aforementioned, thosecompounds possessing a main component which comprises at least onecomponent selected from among the group comprising SiO₂ and Al₂O₃, arepreferred.

In addition, either a thermoplastic resin or thermosetting resin may beused as the aforementioned organic compound, concrete examples of whichmay include a particulate polyolefin, polyester, polyamide, poly(vinylchloride), poly(methyl (meth)acrylate), polystyrene, polynorbornene,various natural high polymer, mixtures thereof, and the like.

The aforementioned inorganic carrier and/or particulate polymer carriermay be used in its intrinsic state “as is”, but is preferably used as acomponent a5 after contact treatment with an organic aluminum compound,modified organic aluminum compound containing Al—O—Al bonds, and thelike, as preliminary treatment.

The ethylene copolymer (A) employed in the present invention may bemanufactured such that the halogen concentration is 10 ppm or less,preferably 5 ppm or less, and more preferably, substantially none (2 ppmor less), by means of using an aforementioned catalyst which does notcontain a halogen such as chlorine or the like, in these components.

By means of using this type of ethylene copolymer (A) which is free ofhalogen such as chlorine and the like, it becomes unnecessary to addadditives and the like, such as a halogen acceptor, which negativelyimpact the dielectric loss tangent, and the like.

The method for manufacturing the ethylene copolymer (A) employed in thepresent invention includes a gas phase polymerization, wherein thesolvent does not exist in substantial amounts, slurry polymerization,solution polymerization, and the like, in the presence of theaforementioned catalyst. Herein, the ethylene copolymer (A) ismanufactured with essentially no oxygen, water, or the like, in thepresence or absence of an inactive hydrocarbon solvent includingaliphatic hydrocarbons such as butane, pentane, hexane, heptane, and thelike, aromatic hydrocarbons such as benzene, toluene, xylene, and thelike, and alicyclic hydrocarbons such as cyclohexane, methylcyclohexane,and the like. The polymerization conditions in the aforementioned arenot particularly limited. However, the polymerization temperature isnormally 15 to 350° C., preferably 20 to 200° C., and more preferably 50to 110° C. The polymerization pressure is normally in the range ofnormal pressure to 70 kg/cm²G, and preferably normal pressure to 20kg/cm²G, in the low or medium pressure process. In addition, thepolymerization pressure is normally 1500 kg/cm²G or less in the highpressure process. The duration of polymerization is normally 3 minutesto 10 hours, and preferably 5 minutes to 5 hours, in the low or mediumpressure process. This duration of polymerization is normally 1 to 30minutes, and preferably 2 to approximately 20 minutes, in the highpressure process. In addition, the method for polymerization is notparticularly limited, and includes multi-step polymerization comprisingtwo or more steps, in which the polymerization conditions such as thehydrogen concentration, monomer concentration, polymerization pressure,polymerization temperature, catalyst, and the like, differ in each step.In addition, the method of polymerization may also include a one-steppolymerization method.

The resin material for an electrical insulating material according tothe present invention comprises the resin component comprising mainlythe aforementioned ethylene copolymer (A), and said resin componentcontains at least one unit (B) derived from at least one type of monomerselected from among a carbonyl or carbonyl derivative group-containingmonomer (M1), a hydroxyl group-containing monomer (M2), a nitrogroup-containing monomer (M3), a nitrile group-containing monomer (M4),and an aromatic ring-containing monomer (M5), wherein the concentrationthereof ranges from 5×10⁻⁷ to 5×10⁻³ mol per one gram of the resincomponent; or said resin component comprises a copolymer or compositionwhich contains a compound or monomer containing two or more ethyleniclinkages (M6), wherein at least 0.8 ethylenic bonds are present per 1000carbon atoms of the resin component.

Concrete examples of the aforementioned carbonyl or carbonyl derivativegroup-containing monomer (M1) may include unsaturated carbonic acidsderived from α,β-unsaturated carbonic acid, unsaturated carbonate estersderived from α,β-unsaturated carbonate ester, vinyl ester monomers, andthe like.

Concrete examples of the aforementioned unsaturated carbonic acid mayinclude, for example, acrylic acid, methacrylic acid, maleic acid,fumaric acid, itaconic acid, and the like. Among the aforementioned,(meth)acrylic acid is effective in improving the volume resistivity, andis thus preferred. Concrete examples of the unsaturated carbonate estermay include unsaturated carbonate esters such as methyl acrylate, methylmethacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate,propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, n-butylacrylate, n-butyl methacrylate, cyclohexyl acrylate, cyclohexylmethacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate,stearyl methacrylate, maleate monomethylester, maleate monoethylester,maleate diethylester, fumarate monomethylester, glycidyl acrylate,glycidyl methacrylate, and the like.

Concrete examples of the aforementioned vinyl ester may include vinylpropionate, vinyl acetate, vinyl capronate, vinyl caprylate, vinyllaurylate, vinyl stearate, vinyl trifluoroacetate, and the like. Amongthe aforementioned, vinyl acetate is preferred.

Examples of the acid anhydride group-containing monomer, which is acarbonyl derivative group-containing monomer, may include maleicanhydride, itaconic anhydride, himic anhydride, methylmaleic anhydride,dimethylmaleic anhydride, phenylmaleic anhydride, diphenylmaleicanhydride, chloromaleic anhydride, dichloromaleic anhydride,fluoromaleic anhydride, difluoromaleic anhydride, bromomaleic anhydride,dibromomaleic anhydride, and the like. Among the aforementioned, maleicanhydride is particularly preferred due to its effectiveness inimproving the volume resistivity.

Examples of the aforementioned other monomers may include carbonmonoxide, methylvinyl ketone, isopropenylvinyl ketone, ethylvinylketone, phenylvinyl ketone, t-butylvinyl ketone, isopropylvinyl ketone,methylpropenyl ketone, methylisopropenyl ketone, cyclohexylvinyl ketone,and the like.

Examples of the hydroxyl group-containing monomer (M2) may include vinylalcohol, 1-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate,hydroxyethyl (meth)acrylate, and the like.

Examples of the nitro group-containing monomer (M3) may include2,4-dinitrophenylacrylate, 2-nitrostyrene, m-nitrostyrene,o-nitrostyrene, p-nitrostyrene, p-nitrophenylmethacrylate,m-nitrophenylmethacrylate, 2,4-dinitrophenylmethacrylate,2,4,6-trinitrophenylmethacrylate, and the like.

Examples of the nitrile group-containing monomer (M4) may includeacrylonitrile, methacrylonitrile, α-methoxyacrylonitrile, vinylidenecyanide, cinammonitrile, crotononitrile, α-phenyl crotononitrile,fumaronitrile, allylacetonitrile, 2-butenenitrile, 3-butenenitrile, andthe like.

The aromatic ring-containing monomer (M5) is a compound containing amonocyclic or polycyclic aromatic ring, which comprises a monomercontaining an ethylenic linkage.

The aforementioned aromatic ring-containing monomer is preferably acompound comprising an aromatic group, containing 1 to 3 rings, concreteexamples of which may include styrene or derivatives thereof,allylbenzene, allyl biphenyl, methylstyrene, allyl benzonate,vinylnaphthalene, 4-phenyl-1-butene, benzyl methacrylate,1,1-diphenylethylene, 1-phenyl-1-tolylethylene, 1-phenyl-1-styrilethane, 1-tolyl-1-styril ethane, 2,4-diphenyl-1-butene,2,4-diphenyl-1-pentene, 2,4-diphenyl-4-methyl-1-pentene, and the like.

Among the aforementioned, styrene is preferred in the present inventiondue to its favorable electrical properties and economical nature.

The amount of these monomers, (M1) to (M5), should be in the range of5×10⁻⁷ to 5×10⁻³ mol, and preferably 1×10⁻⁶ to 1×10⁻⁴ mol, per one gramof the resin component.

In particular, when these monomers (M1) to (M4) such as maleic anhydrideor the like fall below the range of 5×10⁻⁷ mol, improvements in thevolume resistivity are not possible. In addition, in the case of (M5),improvement in the dielectric breakdown strength is likewise notobserved. Furthermore, when the aforementioned monomers exceed 5×10⁻³mol, the processability deteriorates and the volume resistivity drops,both of which are undesirable.

Concretely, the respective methods for introducing these aforementionedmonomers (M1) to (M5) into the resin components are performed by meansof the methods described by (C) or (D) below.

(C): The resin component comprises at least one entity selected fromamong (C1) to (C3), or alternatively comprises blending at least one ofthe aforementioned into the resin component.

(C1) a graft copolymer obtained by means of modifying an ethylenecopolymer (A) using at least one monomer selected from (M1) to (M4).

(C2) a graft copolymer obtained by means of modifying another polyolefin(A′) using at least one monomer selected from (M1) to (M4).

(C3) a random copolymer comprising ethylene and at least one monomerselected from (M1) to (M4); or a random copolymer comprising ethylene,another olefin and at least one monomer selected from (M1) to (M4).

(D): At least one component selected from among (D1) to (D6) is blendedinto the resin component.

(D1) a polymer containing an aromatic ring.

(D2) a random copolymer comprising ethylene, at least one monomerselected from (M1) to (M4), and an aromatic ring-containing monomer(M5); or a random copolymer comprising ethylene, another olefin, atleast one monomer selected from (M1) to (M4), and an aromaticring-containing monomer (M5).

(D3) a graft copolymer obtained by means of modifying an ethylenepolymer containing an aromatic ring using at least one monomer selectedfrom (M1) to (M4).

(D4) a graft copolymer obtained by means of modifying a random polymercomprising ethylene and at least one monomer selected from (M1) to (M4),or a random copolymer comprising ethylene, another olefin, and at leastone monomer selected from (M1) to (M4), using the aromaticring-containing monomer (M5).

(D5) a graft copolymer obtained by means of modifying the ethylenecopolymer (A) using an aromatic ring-containing monomer (M5).

(D6) a graft copolymer obtained by means of modifying the ethylenecopolymer (A) using at least one monomer selected from (M1) to (M4) andaromatic ring-containing monomer (M5).

Concrete examples of the aforementioned graft copolymer (C1) obtained bymeans of modifying the ethylene copolymer (A) using at least onefunctional group-containing monomer (M1) to (M4) may include a graftcopolymer modified using maleic anhydride or acrylic acid. Among these,the maleic anhydride-modified ethylene copolymer (A) is preferably useddue to its effectiveness in improving the volume resistivity.

Concrete examples of the graft copolymer (C2) obtained by means ofmodifying another polyolefin (A′) using at least one monomer selectedfrom (M1) to (M4), and the random copolymer (C3) comprising ethylene andat least one monomer selected from (M1) to (M4), or random copolymer(C3) comprising ethylene, another olefin and at least one monomerselected from (M1) to (M4), may include linear low density polyethylenesmodified using acrylic acid or maleic anhydride; high and medium densitypolyethylenes modified using acrylic acid or maleic anhydride;copolymers of ethylene and acrylic acid or maleic anhydride; copolymersof ethylene and carbon monoxide; an ethylene-methylvinyl ketonecopolymer; an ethylene-ethylvinyl ketone copolymer; anethylene-methylisopropenyl ketone copolymer; an ethylene-hydroxyethyl(meth)acrylate copolymer; an ethylene-2-nitrostyrene copolymer; anethylene-m-nitrostyrene copolymer; an ethylene-p-nitrophenylmethacrylatecopolymer; an ethylene-(meth)acrylonitrile copolymer; anethylene-allylacetonitrile copolymer; a styrene-modified high pressureprocess low density polyethylene; and the like.

The aforementioned polymer (D1) containing aromatic ring group is ahomopolymer comprising a monomer, containing a homocyclic or polycyclicaromatic ring group, copolymer comprising said monomer and olefin, orcopolymer comprising said monomer and a monomer containing a functionalgroup.

The aforementioned aromatic ring-containing monomer is preferably anaromatic group compound comprising 1 to 3 rings, concrete examples ofwhich may include styrene or derivatives thereof, allylbenzene,allylbiphenyl, methylstyrene, allyl benzonate, vinylnaphthalene,4-phenyl-1-butene, benzyl methacrylate, 1,1-diphenylethylene,1-phenyl-1-tolylethylene, 1-phenyl-1-styril ethane, 1-tryl-1-styrilethane, 2,4-diphenyl-1-butene, 2,4-diphenyl-1-pentene,2,4-diphenyl-4-methyl-1-pentene, and the like.

Among these aromatic ring group-containing copolymers, polystyrene,ethylene-styrene random copolymers, and styrene-maleic anhydridecopolymers are most preferred, due to their ease of manufacturing, andeffectiveness in improving the dielectric breakdown strength.

Concrete examples of the aforementioned random copolymer (D2) comprisingan ethylene, at least one monomer selected from (M1) to (M4), and anaromatic ring-containing monomer (M5), or a random copolymer (D2)comprising ethylene, another olefin, at least one monomer selected from(M1) to (M4), and the aromatic ring-containing monomer (M5) may includean ethylene-styrene-maleic anhydride random copolymer, and anethylene-allylbenzene copolymer.

Concrete examples of the copolymer comprising at least one monomercontaining a styrene derivative and ethylene may include anethylene/vinyl acetate/styrene copolymer, an ethylene/vinylacetate/a-methylstyrene copolymer, an ethylene/ethyl acrylate/styrenecopolymer, an ethylene/ethyl acrylate/a-methylstyrene copolymer, and thelike.

Concrete examples of the aforementioned graft copolymer (D3) obtained bymeans of modifying the aforementioned aromatic ring group-containingethylene copolymer using at least one monomer selected from (M1) to (M4)may include a maleic anhydride-modified ethylene-styrene copolymer, amaleic anhydride-modified ethylene-benzyl methacrylate copolymer, and amaleic anhydride-modified ethylene-allylstyrene copolymer.

Concrete examples of the aforementioned graft copolymer (D4) obtained bymeans of modifying the aforementioned random copolymer of ethylene andat least one monomer selected from (M1) to (M4), or random copolymer ofethylene, other olefin, and at least one monomer selected from (M1) to(M4), using the aromatic ring-containing monomer (M5) may includestyrene-modified ethylene-maleic anhydride copolymer.

Examples of the aforementioned graft olefin copolymer (D5) obtained bymeans of modifying the ethylene copolymer (A) using the aromaticring-containing monomer (M5) may include a styrene-modified ethylenecopolymer (A), which is easy to manufacture, and effective in improvingelectrical insulating breakdown strength.

Concrete examples of the aforementioned graft copolymer (D6) obtained bymeans of modifying the ethylene copolymer (A) using at least one monomerselected from (M1)˜(M4), and the aromatic ring-containing monomer (M5)may include an ethylene copolymer (A) modified using maleic anhydrideand styrene.

According to the present invention, the mixing amount of at least onecomponent (D), selected from among the polymers containing an aromaticring group (D1); a random copolymer (D2) comprising ethylene, at leastone monomer selected from (M1) to (M4), and the aromatic ring-containingmonomer (M5), or random copolymer (D2) comprising ethylene, anotherolefin, at least one monomer selected from (M1) to (M4), and thearomatic ring-containing monomer (M5); the graft copolymer (D3) obtainedby means of modifying an ethylene polymer containing an aromaticgroup-ring using at least one monomer selected from (M1) to (M4); thegraft copolymer (D4) obtained by means of modifying a random polymercomprising ethylene and at least one monomer selected from (M1) to (M4),or random copolymer comprising ethylene, another olefin, and at leastone monomer selected from (M1) to (M4), using the aromaticring-containing monomer (M5); the graft copolymer (D5) obtained by meansof modifying the ethylene copolymer (A) using an aromaticring-containing monomer (M5); the graft copolymer (D6) obtained by meansof modifying the ethylene copolymer (A) using at least one monomerselected from (M1) to (M4) and the aromatic ring-containing monomer(M5), is adjusted such that the amount of the aromatic ring-containingmonomer in the aforementioned resin components is in the range of 5×10⁻⁷to 5×10⁻³ mol per one gram of the resin component, and preferably 1×10⁻⁶to 1×10⁻⁴ mol per one gram of the resin component. When theconcentration of the aforementioned monomer is less than 5×10⁻⁷ mol,dielectric breakdown strength cannot be improved.

The method for introducing the compound or monomer (M6) containing twoor more ethylenic linkages into the resin components according to thepresent invention comprises a method in which one component selectedfrom among the components described in the following (E1) to (E5) ismixed into the resin component. When introducing a compound or monomer(M6) containing two or more ethylenic linkages into the resin component,it is preferable to use a cross-linked resin material.

(E) comprises at least one component selected from among (E1) to (E5)below:

(E1) a homopolymer comprising a monomer containing two or more ethyleniclinkages, or copolymer comprising ethylene and monomer containing two ormore ethylenic linkages.

(E2) a graft copolymer obtained by means of modifying a homopolymercomprising a monomer containing two or more ethylenic linkages, orcopolymer comprising ethylene and monomer containing two or moreethylenic linkages, using at least one monomer selected from among theaforementioned (M1) to (M5).

(E3) a random copolymer comprising a monomer containing two or moreethylenic linkages and at least one monomer selected from among theaforementioned (M1) to (M5).

(E4) a random copolymer comprising a monomer containing two or moreethylenic linkages, ethylene, and at least one monomer selected fromamong the aforementioned (M1) to (M5).

(E5) a compound containing two or more ethylenic linkages.

In the aforementioned, by means of employing a homopolymer (E1)comprising a monomer containing two or more ethylenic linkages, orcopolymer (E1) comprising ethylene and monomer containing two or moreethylenic linkages, a sufficient number of ethylenic linkages should bepresent after polymerization. The presence of the aforementionedethylenic linkages allows for the cross-linking properties to be fullyexhibited. Examples of the aforementioned component (E1) may include anliquid oligomer or polymer with an average molecular weight of 1000 to200000, and the like.

Examples of one of the aforementioned components (E1), the homopolymercomprising a monomer containing two or more ethylenic linkages, mayinclude a polymer comprising a C₄₋₁₀ diene. The diene may compriseeither a ring- or straight chain-structure, as long as the ethyleniclinkages are relevant to the polymerization. Among such polymers, abutadiene oligomer, and polybutadiene, with an average molecular weightof approximately 1000 to 200000 are most preferred due to their superiorelectrical insulating properties after cross-linking in addition totheir cross-linking efficiency.

Concrete examples of the aforementioned diene may include 1,3-butadiene,1,3-pentadiene, 1,4-pentadiene, 2-methyl-1,3-butadiene, 1,3-hexadiene,1,4-hexadiene, 1,5-hexadiene, 2,4-hexadiene, 2,3-dimethyl-1,3-butadiene,2-ethyl-1,3-butadiene, 1,3-heptadiene, 1,4-heptadiene,3-(2-propenyl)-cyclopentene, 2-(cyclopentyl)-1,3-butadiene, and thelike. In addition, triene and tetraene, which are polymerized fromdienes, may also be used. Among these, a homopolymer of 1,3-butadiene isparticularly preferred due to its superior cross-linking properties.

Preferred examples of one the aforementioned components (E1), the randomcopolymer comprising ethylene and a monomer containing two or moreethylenic linkages, may include an ethylene-allyl (meth)acrylatecopolymer, an ethylene-vinyl (meth)acrylate copolymer and the like,which are easy to manufacture and superior electrical insulatingproperties after cross-linking and cross-linking efficiency. Thesecopolymers may also be used in combination of two or more.

Concrete examples of the aforementioned graft copolymer (E2) obtained bymeans of modifying a homopolymer comprising a monomer containing two ormore ethylenic linkages, or copolymer comprising ethylene and monomercontaining two or more ethylenic linkages, using at least one monomerselected from among the aforementioned (M1) to (M5); the aforementionedrandom copolymer (E3) comprising a monomer containing two or moreethylenic linkages and at least one monomer selected from among theaforementioned (M1) to (M5); the aforementioned random copolymer (E4)comprising a monomer containing two or more ethylenic linkages,ethylene, and at least one monomer selected from among theaforementioned (M1) to (M5), may include a polybutadiene modified usingacrylic acid or maleic anhydride, a maleic anhydride-modifiedethylene-allyl (meth)acrylate copolymer, a maleic anhydride-modifiedethylene-vinyl (meth)acrylate copolymer, a maleic anhydride-butadienecopolymer, an ethylene-butadiene-maleic anhydride copolymer, and thelike. Among the aforementioned, the maleic anhydride-modifiedpolybutadiene is preferred due to its favorable electrical insulatingproperties after cross-linking, cross-linking efficiency, and effects inimproving the volume resistivity.

Concrete examples of the aforementioned compound (E5) containing two ormore ethylenic linkages may include multi-functional methacrylatemonomers such as trimethylol propane trimethacrylate, ethylene glycoldimethacrylate, diethylene glycol dimethacrylate, and the like;multifunctional vinyl monomers such as triallyl isocyanurate,diallylphthalate, vinylbutyrate, and the like; bismaleimides such asN,N′-m-phenylene bismaleimide, and N,N′-ethylene bismaleimide; dioximessuch as p-quinone dioxime, and the like; divinyl compounds such asdivinyl benzene, 1,5-hexanediene-3-ine, hexatriene, divinyl ether,divinyl sulfone, and the like; and diallyl compounds such as allylstyrene, 2,6-diacrylphenol, diallyl carbinol, and the like.

The mixing amount of at least one the component (M6), selected fromamong the homopolymer (E1) comprising a monomer containing two or moreethylenic linkages, or copolymer (E1) comprising ethylene and monomercontaining two or more ethylenic linkage; the graft copolymer (E2)obtained by means of modifying a homopolymer comprising a monomercontaining two or more ethylenic linkages, or copolymer comprisingethylene and monomer containing two or more ethylenic linkages, using atleast one monomer selected from among the aforementioned (M1) to (M5);the random copolymer (E3) comprising a monomer containing two or moreethylenic linkages and at least one monomer selected from among theaforementioned (M1) to (M5); the random copolymer (E4) comprising amonomer containing two or more ethylenic linkages, ethylene, and atleast one monomer selected from among the aforementioned (M1) to (M5);and the compound (E5) containing two or more ethylenic linkages, isadjusted such that the number of the ethylenic linkages present prior tocross-linking is 0.8 or more per 1000 carbon atoms in the resincomposition. The aforementioned number of the ethylenic linkages ispreferably in the range of 0.8 to 4.0 per 1000 carbon atoms. Forexample, in the high pressure process low density polyethylene, a largenumber of these ethylenic linkages is generally present even if thecomponent (M6) is not blended. Accordingly, the number of the ethyleniclinkages is the overall total of these ethylenic linkages.

The aforementioned ethylenic linkages function as cross-linking pointsat the time of performing cross-linking, and hence they improving thecross-linking efficiency. In addition, at the time of cross-linking, theresidues of the cross-linking agent are incorporated into the mainchain. The residues floating in the resin components are broken down viaions formed by means of both thermal and electrical fields, therebyacquiring charges, which in turn lead to a reduction of the volumeresistivity. Consequently, by means of taking in these residues into themain chain, the aforementioned effects are prevented, which in turnimproves the volume resistivity.

If the number of the aforementioned ethylenic linkages is less than 0.8per 1000 carbon atoms, the cross-linking efficiency is not improved; onthe other hand, a number exceeding 4.0 per 1000 carbon atoms leads toexcessive cross-linking, and deterioration of the mechanical propertiesand processability thereof.

In addition, among these ethylenic linkages, it is particularlypreferred that the number of terminal vinyl groups is in the range of0.5 to 3.0, due to improvements in cross-linking efficiency.

When using a graft modified (co)polymer for introducing theaforementioned component (B) into the resin component, the graftmodified (co)polymer is manufactured in the presence of a radicalinitiator, according to a melting method wherein the (co)polymer isreacted within the extrusion device, and a solution method wherein the(co)polymer is reacted in a solution, or the like.

Examples of the radical initiator may include organic peroxides, dihydroaromatic compounds, dicumyl compounds, and the like.

Preferred examples of the aforementioned organic peroxide may includehydroperoxide, dicumyl peroxide, t-butylcumyl peroxide, dialkyl(allyl)peroxide, diisopropylbenzene hydroperoxide, dipropionyl peroxide,dioctanoyl peroxide, benzoyl peroxide, peroxy succinate, peroxy ketal,2,5-dimethyl-2,5-di-(t-butylperoxy) hexane,2,5-dimethyl-2,5-di-(t-butylperoxy) hexine, t-butylperoxy acetate,t-butylperoxy isobutylate, and the like.

Examples of the dihydro aromatic compounds may include hydroquinoline,derivatives thereof, dihydrofuran, 1,2-dihydrobenzene,1,2-dihydronaphthalene, 9,10-dihydrophenanthrene, and the like.

Examples of the dicumyl compound may include2,3-dimethyl-2,3-diphenylbutane, 2,3-diethyl-2,3-diphenylbutane,2,3-diethyl-2,3-di(p-methylphenyl)butane,2,3-diethyl-2,3-di(bromophenyl)butane, and the like. Among theaforementioned compounds, 2,3-dimethyl-2,3-diphenylbutane isparticularly preferred.

The resin component according to the present invention may contain otherpolyolefins (A′), in addition to the aforementioned ethylene copolymer(A). In such cases, the resin component preferably contains 2% by weightor greater of the ethylene copolymer (A), and 98% by weight or less ofthe other polyolefin (A′).

Examples of the other polyolefin (A′) employed in the present inventionmay include an ethylene (co)polymers obtained by means of the highpressure radical polymerization; ethylene polymers such as very lowdensity polyethylene, linear low density polyethylene, medium to highdensity polyethylene, and the like, which may be obtained under low,medium, or high pressure by means of using a Ziegler catalyst, aPhillips catalyst, other metallocene catalyst, or the like; ahomopolymer or alternating copolymer of C₃₋₁₂ α-polyolefin; and thelike. Among the aforementioned polymers, polyethylenes obtained by meansof the high pressure radical polymerization, medium to high densitypolyethylenes, linear low density polyethylenes, and mixtures of two ormore of these polyethylenes, are particularly preferred due to theirfavorable extrusion-forming properties.

Examples of the other polyolefin (A′) employed in the present inventionmay include an ethylene (co)polymers obtained by means of the highpressure radical polymerization; ethylene polymers such as very lowdensity polyethylene, linear low density polyethylene, medium to highdensity polyethylene, and the like, which may be obtained under low,medium, or high pressure by means of using a Ziegler catalyst, aPhillips catalyst, other metallocene catalyst, or the like; ahomopolymer or alternating copolymer of C₃₋₁₂ α-olefin and the like.Among the aforementioned polymers, polyethylenes obtained by means ofthe high pressure radical polymerization, medium to high densitypolyethylenes, linear low density polyethylenes, and mixtures of two ormore of the polyethylenes, are particularly preferred due to theirfavorable extrusion-forming properties.

The aforementioned medium to high density polyethylenes and linear lowdensity polyethylenes comprise an ethylene homopolymer or ethyleneα-olefin copolymer possessing a density of 0.86 to 0.97 g/cm³, i.e., anethylene homopolymer or ethylene C₃₋₁₂ α-olefin copolymer obtained bymeans of using a Ziegler catalyst, a Phillips catalyst, or othermetallocene catalyst according to the low, medium, or high pressureprocess, or alternatively another conventional method.

Concrete examples of the α-olefin used in the aforementionedpolymerization may include propylene, 1-butene, 4-methyl-1-pentene,1-hexene, 1-octene, 1-dodecene, and the like. Among the aforementionedcompounds, preferred examples include 1-butene, 4-methyl-1-pentene,1-hexene, and 1-octene. Furthermore, 1-butene is particularly preferred.The amount of α-olefin in the ethylene copolymer is preferably 0.5 to 40mol %.

Concrete examples of the preferred combinations in the present inventionare described in the following.

<Preferred Example 1> a graft copolymer (C11) obtained by means ofmodifying the ethylene copolymer (A) using a functional group-containingmonomer (M1). Concrete examples include a maleic anhydride-modifiedethylene copolymer (A).

<Preferred Example 2> a composition of the ethylene copolymer (A); and agraft copolymer (C11) obtained by means of modifying the ethylenecopolymer (A) using the functional group-containing monomer (M1), and/ora graft copolymer (C21) obtained by means of modifying the otherpolyolefin (A′) using the functional group-containing monomer (M1).Concrete examples may include a composition of the ethylene copolymer(A); and the maleic anhydride-modified ethylene copolymer (A), and/ormaleic anhydride-modified low density polyethylene.

<Preferred Example 3> a composition of the other polyolefin (A′), andthe graft copolymer (C11) obtained by means of modifying the ethylenecopolymer (A) using the functional group-containing monomer (M1).Concrete examples may include a composition of a low-densitypolyethylene and the maleic anhydride-modified ethylene copolymer (A).

<Preferred Example 4> a composition of the ethylene copolymer (A); theother polyolefin (A′); and the graft copolymer (C11) obtained by meansof modifying the ethylene copolymer (A) using the functionalgroup-containing monomer (M1), and/or the graft copolymer (C21) obtainedby means of modifying the other polyolefin (A′) using the functionalgroup-containing monomer (M1). Concrete examples may include acomposition of the ethylene copolymer (A); low density polyethylene; andthe maleic anhydride-modified ethylene copolymer (A), and/or maleicanhydride-modified low density polyethylene.

<Preferred Example 5> a composition of the ethylene copolymer (A), and agraft copolymer (E21) obtained by means of modifying a homopolymercomprising two or more ethylenic linkages, using the functionalgroup-containing monomer (M1). Concrete examples may include acomposition of the ethylene copolymer (A) and maleic anhydride-modifiedliquid polybutadiene.

<Preferred Example 6> a composition of the ethylene copolymer (A), theother polyolefin (A′), and the graft copolymer (E21) obtained by meansof modifying a homopolymer comprising two or more ethylenic linkages,using the functional group-containing monomer (M1). Concrete examplesmay include a composition of the ethylene copolymer (A), low-densitypolyethylene, and maleic anhydride-modified liquid polybutadiene.

<Preferred Example 7> a composition of the graft copolymer (C11)obtained by means of modifying the ethylene copolymer (A) using thefunctional group-containing monomer (M1), and the homopolymer (E11)comprising a monomer containing two or more ethylenic linkages. Concreteexamples may include a composition of the maleic anhydride-modifiedethylene copolymer (A), and liquid polybutadiene.

<Preferred Example 8> a composition of the ethylene copolymer (A); thegraft copolymer (E21) obtained by means of modifying a homopolymercomprising a monomer containing two or more ethylene linkages, using thefunctional group-containing monomer (M1); and the graft copolymer (C11)obtained by means of modifying the ethylene copolymer (A) using thefunctional group-containing monomer (M1), and/or the graft copolymer(C21) obtained by means of modifying an olefin polymer using thefunctional group-containing monomer (M1). Concrete examples may includea composition of the ethylene copolymer (A); maleic anhydride-modifiedliquid polybutadiene; and the maleic anhydride-modified ethylenecopolymer (A), and/or maleic anhydride-modified low densitypolyethylene.

<Preferred Example 9> a composition of ethylene copolymer (A); otherpolyolefin (A′); the graft copolymer (E21) obtained by means ofmodifying the homopolymer comprising a monomer containing two or moreethylenic linkages; and the graft copolymer (C11) obtained by means ofmodifying the ethylene copolymer (A) using the functionalgroup-containing monomer (M1), and/or the graft copolymer (C21) obtainedby means of modifying the olefin polymer using the functionalgroup-containing monomer (M1). Concrete examples may include acomposition of the ethylene copolymer (A); low density polyethylene;maleic anhydride-modified liquid polybutadiene; and the maleicanhydride-modified ethylene copolymer (A), and/or maleicanhydride-modified low density polyethylene.

<Preferred Example 10> a composition of the ethylene copolymer (A); thecompound (E5) containing two or more ethylenic linkages; and the graftcopolymer (C11) obtained by means of modifying the ethylene copolymer(A) using the functional group-containing monomer (M1), and/or the graftcopolymer (C21) obtained by means of modifying the other polyolefin (A′)using the functional group containing monomer (M1). Concrete examplesmay include a composition of the ethylene copolymer (A); divinylbenzene;and the maleic anhydride-modified ethylene copolymer (A), and/or maleicanhydride-modified low density polyethylene.

<Preferred Example 11> a composition of the ethylene copolymer (A); theother polyolefin (A′); the compound (E5) containing two or moreethylenic linkages; and the graft copolymer (C11) obtained by means ofmodifying the ethylene copolymer (A) using the functionalgroup-containing monomer (M1), and/or the graft copolymer (C21) obtainedby means of modifying the other polyolefin (A′) using the functionalgroup containing monomer (M1). Concrete examples may include acomposition of the ethylene copolymer (A); low density polyethylene;divinylbenzene; and the maleic anhydride-modified ethylene copolymer(A), and/or maleic anhydride-modified low-density polyethylene.

<Preferred Example 12> a composition of the ethylene copolymer (A) andthe aromatic ring-containing polymer (D1). Concrete examples may includethe ethylene copolymer (A), and the ethylene-styrene random copolymer(D1).

<Preferred Example 13> a composition of the ethylene copolymer (A), thegraft copolymer (E21) obtained by means of modifying a homopolymercomprising a monomer containing two or more ethylene linkages, using thefunctional group-containing monomer (M1), and the aromaticring-containing polymer (D1). Concrete examples may include the ethylenecopolymer (A), maleic anhydride-modified liquid polybutadiene, and theethylene-styrene random copolymer.

<Preferred Example 14> a composition of the graft copolymer (C11)obtained by means of modifying the ethylene copolymer (A) using thefunctional group-containing monomer (M1), and the aromaticring-containing polymer (D1), or, additionally, the graft copolymer(C21) obtained by means of modifying the other polyolefin (A′) using thefunctional group-containing monomer (M1). Concrete examples may includea composition of the maleic anhydride-modified ethylene copolymer (A),and an ethylene-styrene random copolymer.

<Preferred Example 15> a composition of the ethylene copolymer (A), thearomatic ring-containing polymer (D1), and the graft copolymer (D31)obtained by means of modifying an olefin polymer containing an aromaticring group using the functional group-containing monomer (M1). Concreteexamples may include a composition of the ethylene copolymer (A), anethylene-styrene random copolymer, and an ethylene-styrene-maleicanhydride random copolymer or maleic anhydride-modified ethylene-styrenecopolymer.

When using the aforementioned resin material for an electricalinsulating material as an electrical insulating material in the presentinvention, the resin material for an electrical insulating material maybe used in its intrinsic state “as is”, however, it is preferable tocross-link the resin material for an electrical insulating material inorder to further improve the thermal resistance and mechanical strength.The method for cross-linking is not particularly limited, andcross-linking may be performed by means of a radical generator such asorganic peroxide, and the like, electron beam cross-linking, silanecross-linking, and the like. Among the aforementioned methods, themethod in which a radical generator such as organic peroxide, and thelike, is preferred due to its economical nature. In this method, it isparticularly preferred that the aforementioned ethylenic linkages arepresent in the resin component, due to their improved cross-linkingefficiency.

Examples of the aforementioned radical generator may include peroxidessuch as benzoyl peroxide, lauryl peroxide, dicumyl peroxide,t-butylhydro peroxide, α,α-bis(t-butylperoxydiisopropyl) benzene,di-t-butyl peroxide, 2,5-dimethyl-2,5-di-(t-butylperoxy) hexane,2,5-dimethyl-2,5-di-(t-butylperoxy) hexine, azobisisobutylonitrile, andthe like; 2,3-dimethyl-2,3-diphenylbutane;2-3-diethyl-2,3-diphenylbutane; 2,3-diethyl-2,3-di(p-methylphenyl)butane; 2,3-diethyl-2,3-di(bromophenyl) butane; and the like.

In the aforementioned cross-linking, among the aforementioned radicalgenerators, dicumyl peroxide, 2,5-dimethyl-2,5-di-(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy) hexine, and the like, arepreferred. In addition, the amount of the aforementioned radicalgenerator used is within the range of 0.01 to 5 parts by weight, andpreferably 0.1 to 3 parts by weight, per total 100 parts by weight ofthe copolymer or its composition.

In the aforementioned cross-linking, it is rather effective tocross-link using the aforementioned radical generator, after mixing apredetermined amount of at least one component selected from among theaforementioned (E1) to (E5) into the resin component, thereby improvingthe electrical insulating properties such as the volume resistivity andthe like, in addition to increasing the aforementioned thermalresistance and mechanical strength.

As the aforementioned cross-linking agent, the same type of agents thatare used with the radical generator in graft-modifying theaforementioned monomers (M1) to (M5) into the resin component may beemployed. In this case, it is possible to simultaneously blend at leastone monomer selected from among (M1) to (M5) and at least one componentselected from among (E1) to (E5), and thermally mix them in the presenceof the radial generator to simultaneously perform grafting andcross-linking.

In the resin material for an electrical insulating material according tothe present invention, it is possible to add an inorganic filler,organic filler, antioxidant, lubricant, organic or inorganic pigment, UVabsorber, photo-stabilizer, disperser, copper inhibitor, neutralizer,plasticizer, nucleating agent, pigment, and the like, as necessary.

The resin material for an electrical insulating material and electricalinsulating material according to the present invention may be used as ainsulating material for electric wire, cable, and condenser; ainsulating material and distributing cord for high electrical voltagesuch as an X-ray generator, and the like.

The electric wire and cable according to the present invention comprisethe aforementioned resin material for an electrical insulating materialand electrical insulating material, or alternatively, an insulatinglayer in which the same are cross-linked.

Concrete examples of the aforementioned electric wire and cable includean electric cable in which at least the conductor is covered with aninsulating layer comprising the aforementioned resin material for anelectrical insulating material, electrical insulating material, orcross-linked product of the same. It is possible to change the conductorparts into aggregated wires, install a semiconducting layer between theconductor and insulating layer, or alternatively, form a flame retardantresin layer on the outer side of the insulating layer, if necessary.

Concrete examples of the aforementioned electric wire and cable mayinclude a cable comprising a wire which is formed from an aggregate ofcopper wires, a semiconducting layer which is covering the wire andformed by a resin composition to which a conductive carbon or metalpowder has been added, an insulating layer which is covering thesemiconducting layer and formed by the resin material for an electricalinsulating material according to the present invention, a covering orsemiconducting layer which is covering the insulating layer and formedby a metal sheet, and a flame retardant resin or rodent resistance resinwhich is provided on the outermost side; and a cable comprising anaggregate of several or numbers of covered-copper wires and a flameretardant resin or rodent resistance resin which is provided on theoutermost side of said aggregate, wherein said covered-copper wirecomprise a single copper wire, a semiconductor layer which is coveringthe wire and formed by a resin composition to which a carbon or metalpowder is added, an insulating layer which is covering thesemiconducting layer and formed by the resin material for an electricalinsulating material according to the present invention, and a metal filmlayer which is further provided onto said insulating layer; and thelike. The resin material for an electrical insulating material accordingto the present invention provides remarkable effects against hightension electrical power, and is preferably used as a large-capacitycable, and/or a direct current cable.

The present invention relates to the resin material for an electricalinsulating material containing a monomer unit containing ethyleniclinkages and/or a specific functional group in the resin componentcomprising a specific ethylene copolymer (A).

By means of containing the aforementioned specific ethylene copolymer(A), it is possible to improve the processability, thermal resistance,and mechanical strength, and also reduce the temperature dependency ofthe volume resistivity of the resin material for an electricalinsulating material.

Furthermore, the aforementioned functional group functions as a trapsite to prevent charge-transfer. In addition, this functional groupregulates the entrance of charge from the exterior. As a result, it ispossible to improve the volume resistivity and space chargecharacteristics of the resin material for an electrical insulatingmaterial.

In addition, the aforementioned aromatic ring group provides the effectsof absorbing high-energy electrons, diffusing the electron energy as theheat, and emitting low-energy electrons, (i.e., electron energyabsorption effects). In this manner, it is possible to lower theelectron energy, which triggers dielectric breakdown, and thus improvethe dielectric breakdown strength of the resin material for anelectrical insulating material.

The ethylenic linkages function as cross-linking points, and thusimprove the cross-linking efficiency. In addition, at the time ofcross-linking, the residues from the breakdown of the cross-linkingagent are taken into the main chain. The residues floating in the bulkare dissolved via ions produced by means of heat and electrical fieldsto become charged, which leads to a reduction of the volume resistivity.Therefore, by means of taking in the residues into the main chain, it ispossible to prevent such effects, and increase the volume resistivity ofthe resin material for an electrical insulating material.

By means of taking advantages of these aforementioned effects, it ispossible to not only improve the volume resistivity and breakdownstrength, and prevent deterioration of the electric properties aftercrosslinking, but also to dramatically increase the volume resistivityand dielectric strength, when compared with that prior to crosslinking.

EXAMPLES

In the following, the present invention is further described in detail,using the examples. However, the present invention is not limited tothese examples.

The testing method in the present example is described in the following.

(Properties of the Ethylene Copolymer)

[Density]

The measurement of the density was performed according to JIS K6760.

[MFR]

The measurement of the MFR was performed according to JIS K6760.

[Measurement of T_(m1) using DSC]

A sheet with a thickness of 0.2 mm was formed by means of hot pressingthe sample. A test sample of approximately 5 mg was stamped from thissheet, maintained for 10 minutes at 230° C., and then cooled to 0° C. ata cooling rate of 2° C./minute. This material was subsequently re-heatedto 170° C. at a heating rate of 10° C./minute, and the temperature atthe peak of the resulting highest temperature curve was recorded as thehighest peak temperature, T_(m1).

[Mw/Mn]

Mw/Mn was measured using GPC (Type-150C, manufactured by WatersCorporation). ODCB was used at 135° C. as a solvent, and GMH_(HR)-H(S)(manufactured by Toso Corporation) was used as the column.

[TREF]

The sample was injected into the column, maintained at 140° C., andcooled to 25° C. at a cooling rate of 4° C./hour. After the polymer wasdeposited onto glass beads, the column was heated under the followingconditions, to detect the polymer concentration eluted at eachtemperature level, using an infrared detector. Solvent: ODCB; flowspeed: 1 ml/minute; heating rate: 5° C./minute; detector: infraredspectrometer (with a wave number of 2925 cm⁻¹); column: 0.8 cmφ×12 cmL(filled with glass beads); and the concentration of the sample: 1 mg/ml.

[Melt tension]

Melt tension was determined by means of measuring stress when the meltedpolymer was drawn at a constant speed, using a strain gauge. Granulatedpellet was used as a test material, and MT Measuring Device(manufactured by Toyo Seiki Seisaku-Sho, Ltd.) was used as a measuringdevice. The orifice possessed a hole diameter of 2.09 mmφ, and a lengthof 8 mm was used. Measuring conditions were as follows: resintemperature: 190° C.; extrusion speed: 20 mm/minute; and winding speed15 m/minute.

[Chlorine Concentration]

The concentration of the chlorine was measured according to thefluorescence X-ray method, and when the chlorine concentration rose to10 ppm or greater, the detected value was determined as an analysisvalue. When the chlorine concentration was less than 10 ppm, theconcentration was measured using TOX-100-type Chlorine/Sulfur AnalysisDevice (manufactured by Dia Instruments Co., Ltd.). The concentration of2 ppm or less was recorded as ND, and considered as containingessentially no chlorine.

(Electrical Insulating Properties)

[Manufacturing Test Samples for Measuring the Volume Resistivity]

<Non-cross-linked Test Samples>

First, the ethylene copolymer described in the following, or resinmaterial was formed into a sheet with a thickness of 0.3 mm, by means ofhot press processing. The blended materials were in advance kneaded at160° C. for 5 minutes using a plastomill prior to being molded into asheet. Subsequently, the aforementioned sheet was placed betweenaluminum sheets, and the test sample was formed under the followingconditions.

1) The sample was preheated at 140° C. for 5 minutes;

2) The sample was pressurized at 140° C., at 100 kg/cm², for 5 minutes;and

3) The sample was then cooled from 140° C. to 30° C. for 5 minutes underpressure.

<Cross-linked Test Materials>

I. The case in which dicumyl peroxide (hereinafter, referred to as DCP)was used as the cross-linking agent:

The resin material containing 2 parts by weight of DCP to 100 parts byweight of the resin material was kneaded in advance at 120° C., andformed into a sheet with a thickness of 0.3 mm by means of hot pressprocessing. Subsequently, the aforementioned sheet was placed betweenTeflon sheets, and the test sample was formed under the followingconditions.

1) The sample was preheated at 120° C. for 5 minutes;

2) The sample was pressurized at 120° C., at 100 kg/cm², for 5 minutes;

3) The sample was then cooled from 120° C. to 30° C. for 5 minutes. Thesample containing void at this point were removed;

4) The sample was re-heated at 120° C. for 5 minutes;

5) The sample was pressurized at 120° C., at 100 kg/cm², for 5 minutes;

6) The sample was heated from 120° C. to 160° C. under the pressure;

7) The sample was heated at 160° C. for 30 minutes for cross-linking;and

8) The sample was cooled from 160° C. to 30° C. for 5 minutes underpressure.

II. The case in which 2,5-di-methyl-2,5-di(t-butylperoxy) hexine(hereinafter, referred to as PH) was used as the cross-linking agent

The resin material containing 1 part by weight of PH to 100 parts byweight of the resin material was kneaded in advance at 140° C., andformed into a sheet with a thickness of 0.3 mm by means of hot-pressprocessing. Subsequently, the aforementioned sheet was placed betweenTeflon sheets, and the test sample was formed under the followingconditions.

1) The sample was preheated at 140° C. for 5 minutes;

2) The sample was pressurized at 140° C., at 100 kg/cm², for 5 minutes;

3) The sample was cooled from 140° C. to 30° C. for 5 minutes. Thesample containing void at this point were removed;

4) The sample was re-heated at 140° C. for 5 minutes;

5) The sample was pressurized at 140° C., at 100 kg/cm², for 5 minutes;

6) The sample was heated from 140° C. to 180° C. under pressure;

7) The sample was heated at 180° C. for 30 minutes for cross-linking;and

8) The sample was cooled from 180° C. to 30° C. for 5 minutes underpressure.

[Measuring the Volume Resistivity]

The electrode system for measuring the volume resistivity shown in FIG.2 was employed. This electrode system for measuring the volumeresistivity comprised a disc-shaped main electrode 1 and ring-shapedguard electrode 2, which is encompassing the main electrode 1 in theshape of concentric-circle, provided on the surface of the test sample3, and a disc-shaped high voltage electrode 4 provided on the back sideof the test sample 3. The electrode material was made of a stainlesssteel plate, the surface of the electrode material which lay in contactwith the test sample 3 was polished by means of a buff to a mirror-likestate.

The measurements were performed at room temperature (i.e., 20° C.) andat 90° C. under nitrogen atmosphere. In addition, the measurements wereperformed after the test sample was set into the electrode system, andshort-circuited between the main electrode 1 and high voltage electrode4 for 5 minutes to remove the charge on the surface of the test sample3. The test material measured at 90° C. was short-circuited for 7minutes such that the interior of the test sample was uniformly 90° C.

The applied voltage was set at 3300V of direct current provided bybattery. The vibrating reed ammeter, (TR8411 manufactured by AdvantestCorporation), was used as the measuring device. Pipe cable was used forconnecting the measuring device and electrodes, and noise from outsidewas removed. This measuring system was able to measure reliably up to3×10¹⁷Ω at room temperature, and 3×10¹⁶Ω at 90° C. The thickness of thetest samples 3 was approximately 0.3 mm, and the thickness of each testsample was measured up to 2 digits below decimal point. The polarelectrode area was 19.6 cm². From investigation of the current-timecharacteristics, a time of 10 minutes after voltage applying wasdetermined as the time when the decrease in current due to absorbingcurrents dissipated, such that a reliable measurement of a current wasable to be performed. Accordingly, the current value at 10 minutes aftervoltage applying was recorded; however when the current did notstabilize after 10 minutes, measurements were performed after another 5minutes. Any current which did not stabilize thereafter was removed fromthe test. Based on the current values measured, the volume resistivitywas obtained. Measurements were performed ten times, and the averagevalue thereof was used as data.

[Electrical Activation Energy]

Based on the current values measured for the volume resistivity,electrical activation energy (U) was calculated according to thefollowing Arrhenius' equation.

I∝ exp(−U/kT)

(wherein, I represents current; k represents Boltzmann's constant; and Trepresents absolute temperature.)

[Measuring Breakdown Voltage]

The fixed electrode shown in FIG. 3, a so-called McKeown electrode, wasemployed for measuring the breakdown strength. Ball-shaped electrodes 6and 6, each comprising a stainless steel ball with a diameter of ½ inch,were arranged in a hole with a diameter of ½ inch provided in the centerportion of a substrate 5 made of polymethyl methacrylate. The testmaterial 7 cut into a square of approximately 8˜10 mm with a thicknessof 50 Em, was placed between these ball-shaped electrodes 6 and 6.Subsequently, a deaerated epoxy resin 8 was filled and hardened aroundthe test material 7 and electrodes 6 and 6. McKeown electrodes formed inthis manner were soaked in a container filled with silicone oil, and thecontainer was placed in a thermostatic tank to perform measurements at90° C. The voltage waveform used for breakdown had a negative polarityand an impulse-waveform of 1.2/50 μs, and was observed using anoscilloscope. The voltage waveforms broken down at the wave front wereselected as data to obtain an average value of 20 or greater.

[Measuring Water-treeing]

Measuring of the water-treeing was performed by means of the equipmentshown in FIG. 4. The voltage of 10 kV and 10 kHz was applied to the testsample at room temperature for 30 days. After applying, the test samplewas dyed, and the generation and development of water-treeing wereobserved using a microscope. The water-treeing resistance wasdetermined, using the following criteria: X when the generation anddevelopment of water-treeing was extreme; Δ when water-treeing was notextreme, but observed; and ◯ when no water-treeing was observed. Themeasuring device for water-treeing shown in FIG. 4 comprised a conductorboard 12 installed below the test sample 11 for measuring water-treeing;a container 15 filled with water 13 and installed above the test sample11 for measuring water-treeing; a ground electrode 14 connected to theconductor board 12; and a applying electrode 16 in contact with thewater 13 in the container 15. The bottom part of the container 15comprised the test material 11.

[Measuring Space Charge]

The space charge characteristics were evaluated according to the pulseelectroacoustic charge accumulation method. After applying a directcurrent of 15 kV on a sheet with a electrode diameter of 30 mmφ and athickness of 0.3 mm for 60 minutes, the space charge characteristicswere measured in a short-circuited status. Based on the accumulation ofcharge in the vicinity of the electrode, where distortion such aselectric field stress and relaxation are generated, the space chargecharacteristics was evaluated. The accumulation of charge was evaluated,using following criteria: ◯ when little accumulation was observed;“like-polarity” when a charge with the same polarity as the electrodewas accumulated; and “reverse polarity” when a charge with a differentpolarity from the electrode was accumulated, and the evaluation of spacecharge characteristics was shown based on the total amount of charge.

(The Ethylene Copolymer (A))

[Preparation of Solid Catalyst]

1000 ml of toluene purified under nitrogen, 22 g of tetraethoxyzirconium (Zr(OEt)₄), and 74 g of indene were added to a catalystpreparation device provided with an electromagnetic induction stirrer,and 100 g of tripropyl aluminum was added therein in a dropwise mannerfor 10 minutes while maintaining the temperature at 90° C. The reactionwas subsequently allowed to proceed for 2 hours at the same temperature.After the reactant was cooled to 40° C., 3200 ml of a toluene solutionof methyl aluminoxane (with a concentration of 2.5 mmol/ml) was addedand stirred for 2 hours. Subsequently, after 2000 g of silica, which wasbaked in advance at 450° C. for 5 hours (#952, with a surface area of300 m²/g, manufactured by W. R. Grace & Co.), was added and stirred atroom temperature for 1 hour, blown with nitrogen and then dried underreduced pressure at 40° C., to yield a solid catalyst comprising adesirable fluidity.

[Gas Phase Polymerization]

Copolymerization of ethylene and 1-hexene was performed at apolymerization temperature of 80° C., and total pressure of 20 kgf/cm²G,using a continuous-type, fluidized bed gas phase polymerization device.The aforementioned solid catalyst was continuously supplied forpolymerization such that the ratio of ethylene, 1-hexene, and hydrogenwas kept at a predetermined mol ratio, to yield three-types of theethylene copolymers (A1)˜(A3) shown in Table 1.

TABLE 1 Ethylene copolymer A1 A2 A3 A'4 A'5 Density d (g/cm³) 0.9300.925 0.936 0.911 0.935 MFR (g/10 min) 3.5 2.1 4.2 1.9 2.1 Mw/Mn 2.6 2.62.7 2.6 2.2 TREF peak number 1 1 1 1 1 T₇₅ - T₂₅ (° C.) 12.4 13.2 8.06.4 3.0 (−300 × d + 285) 6.0 7.5 4.2 11.7 4.5 (−670 × d + 644) 20.9 24.316.9 33.6 17.6 T_(ml) (° C.) 124 124 126 103 121 (150 × d − 17) 122.5121.8 123.4 119.7 123.3 Melt tension (g) 0.6 0.8 0.4 0.7 2.1 (log MT)−0.22 −0.10 −0.40 −0.15 0.32 (−0.572 × log MFR + 0.3) −0.01 0.12 −0.060.39 0.12 Chloride concentration ND ND ND ND 15 (ppm) Volume resistivity(Ωcm) 3.5 × 10¹⁸ 2.6 × 10¹⁸ 4.0 × 10¹⁸ 1.0 × 10¹⁸ 4.0 × 10¹⁷ at roomtemperature Volume resistivity (Ωcm) 5.6 × 10¹⁷ 4.1 × 10¹⁷ 6.0 × 10¹⁷1.0 × 10¹⁷ 5.0 × 10¹⁴ at 90° C. Electrical activation 0.24 0.24 0.250.30 0.87 energy (eV)

(Other Polyolefin (A′)) (A′1) a high pressure radical process lowdensity polyethylene (LDPE) having a density of 0.919 g/cm³; an MFR of1.0 g/10 minutes; and a product name of J-Rex LD W2000, manufactured byJapan Polyolefins Co., Ltd.

(A′2) a linear low density polyethylene (LLDPE) having a density of0.921 g/cm; an MFR of 1.0 g/10 minutes; and a product name of J-Rex LLAF3280, manufactured by Japan Polyolefins Co., Ltd.

(A′3) a polypropylene (PP) having a density of 0.905 g/cm³; an MFR of1.5 g/10 minutes; and a product name of J-allomer F120K, manufactured byJapan Polyolefins Co., Ltd.

(A′4) a linear low density polyethylene obtained by a single site-typecatalyst, obtained by means of copolymerizing ethylene and 1-butene,using a catalyst comprising bisindenyl zirconium methyl and methylaluminoxane, according to a gas phase process (See Table 1).

(A′5) a linear low density polyethylene obtained by a metallocenecatalyst with a product name of Affinity HF1030, manufactured by DowChemical Ltd. (See Table 1).

(Component (C))

(C1-1) a maleic anhydride-modified ethylene copolymer. 0.7 parts byweight of maleic anhydride per 100 parts by weight of the sample (A1)and 0.05 parts by weight of 2,5-dimethyl-2,5-di(t-butylperoxy) hexinewere mixed together in advance using a Henschel mixer, and allowed toreact at 230° C. using a twin-screw extruder. Upon analyzing the resultvia infrared spectroscopy, the content of the maleic anhydride per onegram of the polymer was 2.6×10⁻⁵ mol.

(C1-2) a maleic anhydride-modified ethylene copolymer

A maleic anhydride was reacted with the sample (A2) in the same manneras in the aforementioned method. Upon analyzing the result via infraredspectroscopy, the content of the maleic anhydride per one gram of thepolymer was 2.6×10⁻⁵ mol.

(C1-3) an acrylic acid-modified ethylene copolymer

An acrylic acid and dicumyl peroxide were mixed into the sample (A1),and the reaction was allowed to proceed at 200° C., using an extruder.Upon analyzing the result via infrared spectroscopy, the content of theacrylic acid per one gram of the polymer was 3.7×10⁻⁶ mol.

(C2-1) a maleic anhydride-modified high pressure radical process lowdensity polyethylene

0.7 parts by weight of maleic anhydride to 100 parts by weight of thesample (A′1), and 0.05 parts by weight of2,5-dimethyl-2,5-di(t-butylperoxy) hexine were mixed together in advanceusing a Henschel mixer, and allowed to react at 230° C. using atwin-screw extruder. Upon analyzing the result via infraredspectroscopy, the content of the maleic anhydride per one gram of thepolymer was 2.6×10⁻⁵ mol.

(C2-2) an acrylic acid-modified high pressure radical process lowdensity polyethylene

An acrylic acid and dicumyl peroxide were mixed into the sample (A′1),and reacted at 200° C., using an extruder. Upon analyzing the result viainfrared spectroscopy, the content of the acrylic acid per one gram ofthe polymer was 3.4×10⁻⁶ mol.

(C3-1) an ethylene-maleic anhydride random copolymer

380 g of n-hexane, 11 g of a maleic anhydride acetone solution (0.11 gof maleic anhydride), and 2,5-dimethyl-2,5-di(t-butylperoxy) hexine, asa polymerization initiator, were added to an autoclave with a stirrer,substituted with nitrogen comprising a capacity of 3.8 L. Subsequently,after 1700 g of ethylene was added thereto, the polymerization wasperformed at 190° C. at 1600 kgf/cm² for 1 hour, to yield anethylene-maleic anhydride copolymer. Upon analyzing the result viainfrared spectroscopy, the content of the maleic anhydride per one gramof the polymer was 1.6×10⁻³ mol.

(C3-2) an ethylene-vinyl alcohol copolymer (Et-VA1)

An ethylene-vinyl alcohol copolymer was obtained in the same manner asin the aforementioned method. Upon analyzing the result via infraredspectroscopy, the content of the hydroxyl group per one gram of thepolymer was 2.4×10⁻⁴ mol.

(C3-3) an ethylene-nitrostyrene copolymer (Et-NSt)

An ethylene-nitrostyrene copolymer was obtained in the same manner as inthe aforementioned method. Upon analyzing the result via infraredspectroscopy, the content of the nitro group per one gram of the polymerwas 2.4×10⁻⁴ mol.

(C3-4) an ethylene-acrylonitrile copolymer (Et-AN).

An ethylene-acrylonitrile copolymer was obtained in the same manner asin the aforementioned method. Upon analyzing the result via infraredspectroscopy, the content of the nitrile group per one gram of thepolymer was 2.3×10⁻⁴ mol.

(Component (D))

(D1-1) an ethylene-styrene random copolymer (Et-St)

An ethylene-styrene random copolymer was obtained by the high pressureradical process. Upon analyzing the result via infrared spectroscopy,the content of the styrene per one gram of the polymer was 1.6×10⁻³ mol.

(D1-2) a polystyrene.

(D2-1) an ethylene-styrene-maleic anhydride random copolymer

A styrene monomer and maleic anhydride were added to an autoclaveequipped with a stirrer, followed by the addition of ethylene tocommence the polymerization. Upon analyzing the result via infraredspectroscopy, the content of the styrene per one gram of the polymer was1.2×10⁻³ mol, and that of the maleic anhydride was 1.1×10⁻³ mol.

(D3-1) a maleic anhydride-modified ethylene-styrene copolymer

A maleic anhydride was reacted with an ethylene-styrene copolymerobtained by the high pressure radical polymerization, using a dicumylperoxide. Upon analyzing the result via infrared spectroscopy, thecontent of the styrene per one gram of the polymer was 1.5×10 mol, andthat of the maleic anhydride was 2.0×10⁻⁵ mol.

(D4-1) a styrene-modified ethylene-maleic anhydride random copolymer

A maleic anhydride was reacted with an ethylene-styrene copolymerobtained by the high pressure radical polymerization, using a dicumylperoxide. Upon analyzing the result via infrared spectroscopy, thecontent of the styrene per one gram of the polymer was 1.5×10⁻³ mol, andthat of the maleic anhydride was 2.0×10⁻⁵ mol.

(D5-1) a styrene-modified ethylene copolymer

A styrene was reacted with the sample (A1), using a dicumyl peroxide.Upon analyzing the result via infrared spectroscopy, the content of thestyrene per one gram of the polymer was 1.2×10-3 mol.

(D6-1) a styrene- and maleic anhydride-modified ethylene copolymer

Styrene and maleic anhydride were reacted with the sample (A1), using adicumyl peroxide. Upon analyzing the result via infrared spectroscopy,the content of the styrene per one gram of the polymer was 6.9×10⁻⁴ mol,and that of the maleic anhydride was 1.9×10⁻⁵ mol.

(Component (E))

(E1-1) an liquid polybutadiene possessing an average molecular weight of3000; a specific gravity of 0.89 g/cm³; and a product name of NissekiPolybutadiene B-3000, manufactured by Nippon Petrochemicals Co., Ltd.

(E1-2) a butadiene resin possessing a specific gravity of 0.89 g/cm³;and a product name of JSR RB820, manufactured by Japan Synthetic RubberCo., Ltd.

(E1-3) an liquid polyisoprene possessing an average molecular weight of29000; a viscosity of 740 poise/38° C.; and a product name of KurapreneLIR-30, manufactured by Kuraray Co., Ltd.

(E2-1) a maleic anhydride-modified liquid polybutadiene possessing anaverage molecular weight of 3000; and a specific gravity of 0.89 g/cm³;and a product name of Nisseki Polybutadiene M-2000, manufactured byNippon Petrochemicals Co., ltd. Upon analyzing the result via infraredspectroscopy, the content of the maleic anhydride per one gram of thepolymer was 7.0×10⁻² mol.

(E2-2) an acrylic acid-modified liquid polybutadiene possessing anaverage molecular weight of 2000; a specific gravity of 0.91 g/cm³; anda product name of Nisseki Polybutadiene MAC-2000, manufactured by NipponPetrochemicals Co., Ltd. Upon analyzing the result via infraredspectroscopy, the content of the acrylic acid per one gram of thepolymer was 2.2×10⁻⁴ mol.

(E2-3) a maleic anhydride-modified butadiene resin

A butadiene resin was modified using maleic anhydride, while heating bymeans of a single-screw extruder. Upon analyzing the result via infraredspectroscopy, the content of the maleic anhydride per one gram of thepolymer was 3.4×10⁻⁴ mol.

(E2-4) a maleic anhydride-modified liquid polyisoprene

An liquid polyisoprene was modified using maleic anhydride, whileheating by means of using an autoclave. Upon analyzing the result viainfrared spectroscopy, the content of the maleic anhydride per one gramof the polymer was 2.9×10⁻⁴ mol.

(E3-1) a maleic anhydride-modified butadiene copolymer

A butadiene copolymer was modified using maleic anhydride, while heatingby means of using an autoclave. Upon analyzing the result via infraredspectroscopy, the content of the maleic anhydride per one gram of thepolymer was 9.0×10⁻⁵ mol.

(E4-1) a mixture of an ethylene-vinyl alcohol copolymer (with an alcoholresidue per one gram of the copolymer was 1.1×10⁻³ mol), obtained bymeans of hydrolysis following copolymerization of ethylene and vinylalcohol, and a butadiene resin (E1-2).

(E5-1) divinyl benzene.

Examples 1 to 79

The components selected from among the components (A), (C), (D) and (E)were used according to the mixing ratios shown in Tables 2 to 8, andcross-linked, as necessary.

TABLE 2-1 Resin composition Component (A) Component (E) Component (C)Component (D) Parts Parts Parts Parts by by by by Example Type weightType weight Type weight Type weight <1> 1 C1−1 100.0 <1> 2 C1−2 100.0<1> 3 C1−3 100.0 <2> 4 A1 92.0 C1−1 8.0 <2> 5 A1 81.0 C1−1 19.0 <2> 6 A162.0 C1−1 38.0 <2> 7 A1 81.0 C1−2 19.0 <2> 8 A1 70.0 C1−3 30.0 <2> 9 A181.0 C1−2 19.0 <2> 10 A1 92.0 C2−1 8.0 <2> 11 A1 81.0 C2−1 19.0 <2> 12A1 62.0 C2−1 38.0

TABLE 2-2 Resin composition Measurement Number of condition AromaticFunctional group ethylenic Cross- component component linkages (perCross- linking Example (mol/g) Type (mol/g) 1000 C) linking agent <1> 1M1 2.6 × 10⁻⁵ None <1> 2 M1 2.6 × 10⁻⁵ None <1> 3 M1 3.7 × 10⁻⁶ None <2>4 M1 2.0 × 10⁻⁶ None <2> 5 M1 4.9 × 10⁻⁶ None <2> 6 M1 9.8 × 10⁻⁶ None<2> 7 M1 4.9 × 10⁻⁶ None <2> 8 M1 1.1 × 10⁻⁶ None <2> 9 M1 4.9 × 10⁻⁶None <2> 10 M1 2.0 × 10⁻⁶ None <2> 11 M1 4.9 × 10⁻⁶ None <2> 12 M1 9.8 ×10⁻⁶ None

TABLE 3-1 Resin composition Component (A) Component (E) Component (C)Component (D) Parts Parts Parts Parts by by by by Example Type weightType weight Type weight Type weight <2>  13 A2 81.0 C2-1 19.0 <2>  14 A170.0 C2-2 30.0 <2>  15 A3 81.0 C2-1 19.0 <2>' 16 A1 99.6 C3-1 0.4 <2>'17 A1 99.0 C3-2 1.0 <2>' 18 A1 99.0 C3-3 1.0 <2>' 19 A2 99.0 C3-4 1.0<2>' 20 A1 99.0 C3-4 1.0 <3>  21  A'1 81.0 C1-1 19.0 <3>  22  A'1 70.0C1-3 30.0 <3>  23  A'2 81.0 C1-1 19.0

TABLE 3-2 Resin composition Measurement Number of condition AromaticFunctional group ethylenic Cross- component component linkages (perCross- linking Example (mol/g) Type (mol/g) 1000 C) linking agent <2> 13 M1 4.9 × 10⁻⁶ None <2>  14 M1 1.0 × 10⁻⁶ None <2>  15 M1 4.9 × 10⁻⁶None <2>' 16 M1 6.1 × 10⁻⁶ None <2>' 17 M2 2.1 × 10⁻⁶ None <2>' 18 M32.1 × 10⁻⁶ None <2>' 19 M4 2.1 × 10⁻⁶ None <2>' 20 M4 2.1 × 10⁻⁶ None<3>  21 M1 4.9 × 10⁻⁶ None <3>  22 M1 1.0 × 10⁻⁶ None <3>  23 M1 4.9 ×10⁻⁶ None

TABLE 4-1 Resin composition Component (A) Component (E) Component (C)Component (D) Parts Parts Parts Parts by by by by Example Type weightType weight Type weight Type weight <3>  24 A'3 81.0 C1-1 19.0 <3>  25A'4 81.0 C1-1 19.0 <4>  26 A1  8.0 C1-1 19.0 A'4 73.0 <4>  27 A1  8.0C2-1 19.0 A'1 73.0 <4>  28 A2 8.0 C2-1 19.0 A'1 73.0 <4>  29 A1  7.0C2-2 30.0 A'1 63.0 <4>' 30 A1  10.0 C3-1 0.4 A'1 89.6 <4>' 31 A1  9.0C3-2 1.0 A'1 90.0 <4>' 32 A1  9.0 C3-3 1.0 A'1 90.0 <4>' 33 A1  9.0 C3-41.0 A'1 90.0

TABLE 4-2 Resin composition Measurement Number of condition AromaticFunctional group ethylenic Cross- component component linkages (perCross- linking Example (mol/g) Type (mol/g) 1000 C) linking agent <3> 24 M1 4.9 × 10⁻⁶ None <3>  25 M1 4.9 × 10⁻⁶ None <4>  26 M1 4.9 × 10⁻⁶None <4>  27 M1 4.9 × 10⁻⁶ None <4>  28 M1 4.9 × 10⁻⁶ None <4>  29 M11.0 × 10⁻⁶ None <4>' 30 M1 6.0 × 10⁻⁶ None <4>' 31 M2 2.1 × 10⁻⁶ None<4>' 32 M3 2.1 × 10⁻⁶ None <4>' 33 M4 2.1 × 10⁻⁶ None

TABLE 5-1 Resin composition Component (A) Component (E) Component (C)Component (D) Parts Parts Parts Parts by by by by Example Type weightType weight Type weight Type weight <5> 34 A1 99.7 E2-1 0.3 <5> 35 A199.2 E2-1 0.8 <5> 36 A1 98.4 E2-2 1.6 <5> 37 A2 99.7 E2-1 0.3 <5> 38 A399.7 E2-1 0.3 <6> 39 A1 10.0 E2-1 0.3  A'1 89.7 <6> 40 A1 10.0 E2-1 0.8 A'1 89.2 <6> 41 A1 10.0 E2-2 1.6  A'1 88.4 <6> 42 A1 9.0 E2-3 1.0  A'190.0 <6> 43 A1 10.0 E2-4 1.2  A'1 88.8 <6> 44 A1 10.0 E2-1 0.3  A'2 89.7<6> 45 A2 10.0 E2-1 0.3  A'1 89.7

TABLE 5-2 Resin composition Measurement Number of condition AromaticFunctional group ethylenic Cross- component component linkages (perCross- linking Example (mol/g) Type (mol/g) 1000 C) linking agent <5> 34M1 2.0 × 10⁻⁶ 0.8 Present PH <5> 35 M1 5.0 × 10⁻⁶ 1.8 Present PH <5> 36M1 3.5 × 10⁻⁶ 3.0 Present PH <5> 37 M1 2.0 × 10⁻⁶ 0.8 Present PH <5> 38M1 2.0 × 10⁻⁶ 0.8 Present PH <6> 39 M1 2.0 × 10⁻⁶ 0.8 Present DCP <6> 40M1 5.0 × 10⁻⁶ 1.8 Present DCP <6> 41 M1 3.5 × 10⁻⁶ 3.0 Present DCP <6>42 M1 3.3 × 10⁻⁶ 1.9 Present DCP <6> 43 M1 3.4 × 10⁻⁶ 2.1 Present DCP<6> 44 M1 2.0 × 10⁻⁶ 0.8 Present DCP <6> 45 M1 2.0 × 10⁻⁶ 0.8 PresentDCP

TABLE 6-1 Resin composition Component (A) Component (E) Component (C)Component (D) Parts Parts Parts Parts by by by by Example Type weightType weight Type weight Type weight <6>' 46 A1  9.6 E3−1 4.0 A'1 86.4<6>' 47 A1  10.0 E4−1 0.4 A'1 89.6 <7>  48 E1−1 1.0 C1-1 99.0 <7>' 49E2-1 0.3 C1-1 99.7 <7>' 50 E2-1 0.3 C1-2 99.7 <8> 51 A1 89.7 E2-1 0.3C2-1 10.0 <8> 52  A1 89.7 E2-1 0.3 C1-1 10.0 <8>' 53 A'1 89.7 E2-1 0.3C1-1 10.0 <9>  54  A1 9.0 E2-1 0.3 C2-1 10.0 A'1 80.7 <9>  55  A1 8.0E1−1 1.0 C2-1 19.0 A'1 72.0 <9>' 56  A1 8.0 E1−2 1.0 C2-1 19.0 A'1 72.0

TABLE 6-2 Resin composition Measurement Number of condition AromaticFunctional group ethylenic Cross- component component linkages (perCross- linking Example (mol/g) Type (mol/g) 1000 C) linking agent <6>'46 M1 3.5 × 10⁻⁶ 7.6 Present DCP <6>' 47 M2 4.4 × 10⁻⁶ 1.0 Present DCP<7>  48 M1 2.5 × 10⁻⁵ 2.1 Present PH <7>' 49 M1 2.7 × 10⁻⁵ 0.8 PresentPH <7>' 50 M1 2.7 × 10⁻⁵ 0.8 Present PH <8>  51 M1 4.6 × 10⁻⁶ 1.8Present PH <8>  52 M1 4.6 × 10⁻⁶ 0.8 Present PH <8>' 53 M1 4.6 × 10⁻⁶0.8 Present PH <9>  54 M1 4.6 × 10⁻⁶ 0.8 Present DCP <9>  55 M1 4.9 ×10⁻⁶ 2.1 Present DCP <9>' 56 M1 4.9 × 10⁻⁶ 1.9 Present DCP

TABLE 7-1 Resin composition Component (A) Component (E) Component (C)Component (D) Parts Parts Parts Parts by by by by Example Type weightType weight Type weight Type weight <9>' 57 A1 8.0 E1-3 1.0 C2-1 19.0 A'1 72.0 <9>' 58 A3 8.0 E1-1 1.0 C2-1 19.0  A'1 72.0 <10> 59 A1 80.8E5-1 0.2 C1-1 19.0 <10> 60 A1 80.8 E5-1 0.2 C2-1 19.0 <11> 61 A1 8.0E5-1 0.2 C2-1 19.0  A'1 72.8 <12> 62 A1 95.0 D1-1 5.0 <12> 63 A1 90.0D1-1 10.0 <12> 64 A1 50.0 D1-2 50.0 <13> 65 A1 89.7 E2-1 0.3 D1-1 10.0<14> 66 C1-1 19.0 D1-1 81.0 <14>' 67 C1-1 19.0 D5-1 81.0

TABLE 7-2 Resin composition Measurement Number of condition AromaticFunctional group ethylenic Cross- component component linkages (perCross- linking Example (mol/g) Type (mol/g) 1000 C) linking agent <9>'57 M1 4.9 × 10⁻⁶ 2.0 Present DCP <9>' 58 M1 4.9 × 10⁻⁶ 2.1 Present DCP<10> 59 1.5 × 10⁻⁵ M1 4.9 × 10⁻⁶ 0.8 Present PH <10> 60 1.5 × 10⁻⁵ M14.9 × 10⁻⁶ 0.8 Present PH <11> 61 1.5 × 10⁻⁵ M1 4.9 × 10⁻⁶ 0.8 PresentDCP <12> 62 7.8 × 10⁻⁵ None <12> 63 1.5 × 10⁻⁴ None <12> 64 4.8 × 10⁻³None <13> 65 1.5 × 10⁻⁴ M1 2.1 × 10⁻⁶ 0.8 Present PH <14> 66 1.2 × 10⁻³M1 4.9 × 10⁻⁶ None <14>' 67 9.7 × 10⁻⁴ M1 4.9 × 10⁻⁶ None

TABLE 8-1 Resin composition Component (A) Component (E) Component (C)Component (D) Parts Parts Parts Parts by by by by Example Type weightType weight Type weight Type weight <15> 68 A1 90.0 D1-1 5.0 D3-1 5.0<15>' 69 A1 98.0 D2-1 2.0 <15>' 70 A1 95.0 D3-1 5.0 <15>' 71 A1 97.0D4-1 3.0 <15>' 72 A1 90.0 D5-1 10.0 <15>' 73 A1 85.0 D6-1 15.0 <16> 74D5-1 100.0 <16> 75 D6-1 100.0 <17> 76 E1-1 1.0 D5-1 99.0 <17> 77 E1-11.0 D6-1 99.0 <18> 78 A1 99.0 E1-1 1.0 <18> 79 A1 89.0 E1-1 1.0 D1-110.0

TABLE 8-2 Resin composition Measurement Number of condition AromaticFunctional group ethylenic Cross- component component linkages (perCross- linking Example (mol/g) Type (mol/g) 1000 C) linking agent <15>68 1.5 × 10⁻⁴ M1 1.0 × 10⁻⁵ None <15>' 69 2.3 × 10⁻⁵ M1 2.1 × 10⁻⁵ None<15>' 70 7.9 × 10⁻⁵ M1 1.0 × 10⁻⁵ None <15>' 71 4.5 × 10⁻⁵ M1 4.7 × 10⁻⁵None <15>' 72 1.1 × 10⁻⁴ None <15>' 73 1.0 × 10⁻⁴ M1 2.8 × 10⁻⁶ None<16> 74 1.2 × 10⁻³ None <16> 75 6.9 × 10⁻⁴ M1 1.9 × 10⁻⁵ None <17> 761.1 × 10⁻³ 2.1 Present PH <17> 77 6.8 × 10⁻⁴ M1 1.8 × 10⁻⁵ 2.1 PresentPH <18> 78 2.1 Present PH <18> 79 1.5 × 10⁻⁴ 2.1 Present PH

<1> Examples 1 to 3 are graft copolymers (C11) obtained by means ofmodifying the ethylene copolymer (A) using a functional group-containingmonomer (M1), as described in Preferred Example 1, and concretelycomprise a sample selected from (C1-1), (C1-2), and (C1-3),respectively.

The measured results of the electrical insulating properties are shownin Table 9. The volume resistivity, space charge characteristics, andwater-treeing properties all displayed significant improvements.

<2> Examples 4 to 15 represent compositions comprising the ethylenecopolymer (A); and a graft copolymer (C11) obtained by means ofmodifying the ethylene copolymer (A) using a functional group-containingmonomer (M1), and/or a graft copolymer (C21) obtained by means ofmodifying another polyolefin (A′) using a functional group-containingmonomer (M1), as described in Preferred Example 2. Concretely, theseexamples comprise compositions obtained by means of combining of samplesselected from (A1) to (A3), (C1-1) to (C1-3), (C2-1), and (C2-2). Themeasured results of the electrical insulating properties are shown inTables 9 and 10.

<2>′ In addition, Examples 16 to 20 represent compositions comprisingthe ethylene copolymer (A); and a random copolymer (C3) of an olefin andat least one monomer (M1) to (M4). Concretely, these examples comprisecompositions obtained by means of combining of samples selected from(A1), (A2), and (C3-1) to (C3-4).

The measured results of the electrical insulating properties are shownin Table 10. The volume resistivity, space charge characteristics, andwater-treeing properties all displayed significant improvements.

<3> Examples 21 to 25 represent compositions comprising anotherpolyolefin (A′), and a graft copolymer (C11) obtained by means ofmodifying the ethylene copolymer (A) using a functional group-containingmonomer (M1), as described in Preferred Example 3. Concretely, theseexamples comprise compositions obtained by means of combining samplesselected from (A′1) to (A′4), (C1-1), and (C1-3).

The measured results of the electrical insulating properties are shownin Tables 10 and 11. The volume resistivity, space chargecharacteristics, and water-treeing all displayed significantimprovements.

<4> Examples 26 to 29 represent compositions comprising the ethylenecopolymer (A); another polyolefin (A′); and a graft copolymer (C11)obtained by means of modifying the ethylene copolymer (A) using afunctional group-containing monomer (M1), and/or a graft copolymer (C21)obtained by means of modifying another polyolefin using a functionalgroup-containing monomer (M1), as described in Preferred Example 4.Concretely, these examples comprise compositions obtained by means ofcombining samples selected from (A1), (A2), (A′1), (A′4), (C2-1), and(C2-2). The measured results of the electrical insulating properties areshown in Table 11.

<4>′ In addition, Examples 30 to 33 represent compositions comprisingthe ethylene copolymer (A), another polyolefin (A′), and a randomcopolymer (C3) of the olefin and at least one monomer (M1) to (M4).Concretely, these examples comprise compositions formed by means ofcombining samples selected from (A1), (A′1), and (C3-1) to (C3-4).

The measured results of the electrical insulating properties are shownin Table 11. The volume resistivity, space charge characteristics, andwater-treeing all displayed significant improvements.

<5> Examples 34 to 38 represent compositions comprising the ethylenecopolymer (A); and a graft copolymer (E21) obtained by means ofmodifying a homopolymer comprising a monomer containing two or moreethylenic linkages, using a functional group-containing monomer (M1), asdescribed in Preferred Example 5. Concretely, these examples comprisecompositions obtained by means of combining samples selected from (A1)to (A3), (E2-1), and (E2-2). The measured results of the electricalinsulating properties are shown in Table 12. These aforementionedexamples exhibited a high volume resistivity, even after cross-linking,in addition to improved space charge characteristics and water-treeingproperties.

<6> Examples 39 to 45 represent compositions comprising the ethylenecopolymer. (A), another polyolefin (A′), and a graft copolymer (E21)obtained by means of modifying a homopolymer comprising a monomercontaining two or more ethylenic linkages, using a functional-groupcontaining monomer (M1), as described in Preferred Example 6.Concretely, these examples comprise compositions obtained by means ofcombining samples selected from (A1), (A2), (A′1), (A′2), and (E2-1) to(E2-4). The measured results of the electrical insulating properties areshown in Table 12.

<6>′ In addition, Examples 46 and 47 represent compositions comprisingthe ethylene copolymer (A); another polyolefin (A′); and a randomcopolymer (E3) of a monomer containing two or more ethylenic linkagesand at least one monomer of (M1) to (M5), or a random copolymer (E4)comprising a monomer containing two or more ethylenic linkages and atleast one monomer of (M1) to (M5). Concretely, these examples comprisecompositions obtained by means of combining samples selected from (A1),(A′1), (E3-1), and (E4-1).

The measured results of the electrical insulating properties are shownin Table 13. These examples similarly exhibited a high volumeresistivity even after cross-linking, and showed improved space chargecharacteristics and water-treeing properties. The volume resistivityincreased with increases in the proportional content of (E2-1).

<7> Example 48 represents the composition comprising a graft copolymer(C11) obtained by means of modifying the ethylene copolymer (A) using afunctional group-containing monomer (M1), and a homopolymer (E11)comprising a monomer containing two or more ethylenic linkages, asdescribed in Preferred Example 7. Concretely, this example comprisessamples (E1-1) and (C1-1). The measured results of the electricalinsulating properties are shown in Table 13.

<7>′ In addition, Examples 49 and 50 represent the compositioncomprising a graft copolymer (C11) obtained by means of modifying theethylene copolymer (A) using a functional group-containing monomer (M1);and a graft copolymer (E21) obtained by means of modifying a homopolymercomprising a monomer containing two or more ethylenic linkages, using afunctional group-containing monomer (M1). Concretely, these examplescomprise compositions formed by means of combining samples (E2-1), and(C1-1) or (C1-2). The measured results of the electrical insulatingproperties are shown in Table 13. These examples exhibited a high volumeresistivity, even after cross-linking, and also displayed improved spacecharge characteristics and water-treeing properties.

<8> Examples 51 and 52 represent compositions comprising the ethylenecopolymer (A); a graft copolymer (E21) obtained by means of modifying ahomopolymer comprising a monomer containing two or more ethyleniclinkages, using a functional group-containing monomer (M1); and a graftcopolymer (C11) obtained by means of modifying the ethylene copolymer(A) using a functional group-containing monomer (M1), and/or a graftcopolymer (C21) obtained by means of modifying another polyolefin (A′)using a functional group-containing monomer (M1), as described inPreferred Example 8. Concretely, these examples comprise compositionsobtained by means of combining samples selected from (A1), (E2-1),(C1-1), and (C2-1). The measured results of the electrical insulatingproperties are shown in Table 13.

<8>′ In addition, Example 53 represents a composition comprising anotherpolyolefin (A′); a graft copolymer (E21) obtained by means of modifyinga homopolymer comprising a monomer containing two or more ethyleniclinkages, using a functional group-containing monomer (M1); and a graftcopolymer (C11) obtained by means of modifying the ethylene copolymer(A) using a functional group-containing monomer (M1). Concretely, theseexamples comprise compositions obtained by means of combining samples(A′1), (E2-1), and (C1-1).

The measured results of the electrical insulating properties are shownin Table 13. The examples exhibited a high volume resistivity even aftercross-linking, and also displayed improved space charge characteristicsand water-treeing properties.

<9> Examples 54 and 55 represent compositions comprising the ethylenecopolymer (A); another polyolefin (A′); a graft copolymer (E21) obtainedby means of modifying a homopolymer comprising a monomer containing twoor more ethylenic linkages, using a functional group-containing monomer(M1); and a graft copolymer (C21) obtained by means of modifying anotherpolyolefin (A′) using a functional group-containing monomer (M1), asdescribed in Preferred Example 9. Concretely, these examples comprisecompositions obtained by means of combining samples (A1), (A′1), (E2-1),and (C2-1). The measured results of the electrical insulating propertiesare shown in Table 13.

<9>′ In addition, Examples 56 to 58 represent compositions comprisingthe ethylene copolymer (A); another polyolefin (A′); a homopolymer (E11)comprising a monomer containing two or more ethylenic linkages; and agraft copolymer (C21) obtained by means of modifying another polyolefin(A′) using a functional group-containing monomer (M1). Concretely, theseexamples comprise compositions obtained by means of combining samplesselected from (A1), (A3), (A′1), (E1-1) to (E1-3), and (C2-1).

The measured results of the electrical insulating properties are shownin Tables 13 and 14. These examples exhibited a high volume resistivity,even after cross-linking, and also displayed improved space chargecharacteristics and water-treeing properties. <10> Examples 59 and 60represent compositions comprising the ethylene copolymer (A); a compound(E5) containing two or more ethylenic linkages; and a graft copolymer(C11) obtained by means of modifying the ethylene copolymer (A) using afunctional group-containing monomer (M1), or a graft copolymer (C21)obtained by means of modifying another polyolefin (A′) using afunctional group-containing monomer (M1), as described in PreferredExample 10. Concretely, these examples comprise compositions obtained bymeans of combining samples (A1), (ES-1), and (C1-1) or (C2-1).

The measured results of the electrical insulating properties are shownin Table 14. The examples exhibited a high volume resistivity, evenafter cross-linking, and also displayed improved electrical breakdownfield, space charge characteristics and water-treeing properties.

<11> Example 61 represents the composition comprising the ethylenecopolymer (A); another polyolefin (A′); a compound (E5) containing twoor more ethylenic linkages; and a graft copolymer (C21) obtained bymeans of modifying another polyolefin (A′) using a functionalgroup-containing monomer (M1), as described in Preferred Example 11.Concretely, this example comprises a combination of samples (A1), (A′1),(E5-1), and (C2-1).

The measured results of the electrical insulating properties are shownin Table 14. The examples exhibited a high volume resistivity even aftercross-linking, and also displayed improved electrical breakdown field,space charge characteristics and water-treeing properties.

<12> Examples 62 to 64 represent compositions comprising the ethylenecopolymer (A), and an aromatic ring-containing polymer (D1), asdescribed in Preferred Example 12. Concretely, these examples comprisecompositions obtained by means of combining samples (A1), and (D1-1) or(D2-1).

The measured results of the electrical insulating properties are shownin Table 14. The examples exhibited an improved volume resistivity,electrical breakdown field, space charge characteristics andwater-treeing properties.

<13> Example 65 represents a composition comprising the ethylenecopolymer (A); a graft copolymer (E21) obtained by means of modifying ahomopolymer comprising a monomer containing two or more ethyleniclinkages, using a functional group-containing monomer (M1); and anaromatic ring-containing polymer (D1), as described in Preferred Example13. Concretely, this example comprises a combination of samples (A1),(E2-1), and (D1-1).

The measured results of the electrical insulating properties are shownin Table 14. These examples exhibited a high volume resistivity, evenafter cross-linking, and also displayed improved electrical breakdownfield, space charge characteristics and water-treeing properties.

<14> Example 66 represents a composition comprising a graft copolymer(C11) obtained by means of modifying the ethylene copolymer (A) using afunctional group-containing monomer (M1); and an aromaticring-containing polymer (D1), as described in Preferred Example 14.Concretely, this example comprises a combination of samples (C1-1) and(D1-1). The measured results of the electrical insulating properties areshown in Table 14.

<14>′ In addition, Example 67 represents a composition comprising agraft copolymer (C11) obtained by means of modifying the ethylenecopolymer (A) using a functional group-containing monomer (M1); and agraft copolymer (D5) obtained by means of modifying the ethylenecopolymer (A) using an aromatic ring-containing monomer (M5).Concretely, this example comprises a combination of samples (C1-1) and(D5-1).

The measured results of the electrical insulating properties are shownin Table 14. The examples exhibited an improved volume resistivity,electrical breakdown field, space charge characteristics andwater-treeing properties.

<15> Example 68 represents a composition comprising the ethylenecopolymer (A); an aromatic ring-containing polymer (D1); and a graftcopolymer (D31) obtained by means of modifying an olefin polymercontaining an aromatic ring, using a functional group-containing monomer(M1), as described in Preferred Example 15. Concretely, this examplecomprises a combination of samples (A1), (D1-1) and (D3-1).

The measured results of the electrical insulating properties are shownin Table 15. The examples exhibited an improved volume resistivity,electrical breakdown field, space charge characteristics andwater-treeing properties.

<15>′ Examples 69 to 73 represent compositions comprising the ethylenecopolymer (A); and at least one component selected from among a randomcopolymer (D2) of an olefin, at least one monomer selected from (M1) to(M4), and an aromatic ring-containing monomer (M5); a graft copolymer(D3) obtained by means of modifying an olefin polymer containing anaromatic ring, using at least one monomer selected from (M1) to (M4); agraft copolymer (D4) obtained by means of modifying a random copolymerof an olefin and at least one monomer selected from (M1) to (M4), usingan aromatic ring-containing monomer (M5); a graft copolymer (D5)obtained by means of modifying the ethylene copolymer (A) using anaromatic ring-containing monomer (M5); and a graft copolymer (D6)obtained by means of the ethylene copolymer (A) using at least onemonomer selected from (M1) to (M4) and an aromatic ring-containingmonomer (M5). Concretely, these examples comprise compositions obtainedby means of combining a sample (A1) and at least one component selectedfrom among samples (D2-1) to (D6-1).

The measured results of the electrical insulating properties are shownin Table 15. The examples exhibited an improved volume resistivity,electrical breakdown field, space charge characteristics andwater-treeing properties.

<16> Examples 74 and 75 comprise a graft copolymer (D5) obtained bymeans of modifying the ethylene copolymer (A) using an aromaticring-containing monomer (M5); or a graft copolymer (D6) obtained bymeans of the ethylene copolymer (A) using at least one monomer selectedfrom (M1) to (M4) and an aromatic ring-containing monomer (M5).Concretely, these examples comprise compositions a sample (D5-1) or(D6-1).

The measured results of the electrical insulating properties of theseexamples are shown in Table 15. These examples exhibited an improvedvolume resistivity, electrical breakdown field, space chargecharacteristics and water-treeing properties.

<17> Examples 76 and 77 represent compositions comprising a graftcopolymer (D5) obtained by means of modifying the ethylene copolymer (A)using an aromatic ring-containing monomer (M5); or a graft copolymer(D6) obtained by means of the ethylene copolymer (A) using at least onemonomer selected from (M1) to (M4) and an aromatic ring-containingmonomer (M5), and a homopolymer (E11) comprising a monomer containingtwo or more ethylenic linkages. Concretely, these examples comprisecompositions obtained by means of combining samples (E1-1), and (D5-1)or (D6-1).

The measured results of the electrical insulating properties are shownin Table 15. The examples exhibited a high volume resistivity, evenafter cross-linking, and improved electrical breakdown field, spacecharge characteristics and water-treeing properties.

<18> Examples 78 and 79 represent a composition comprising the ethylenecopolymer (A), and a homopolymer (E11) comprising a monomer containingtwo or more ethylenic linkages, or alternatively, a compositioncomprising the ethylene copolymer (A), a homopolymer (E11) comprising amonomer containing two or more ethylenic linkages, and an aromaticring-containing polymer (D1). Concretely, these examples comprisecompositions obtained by means of combining samples (A1) and (E1-1), orsamples (A1), (E1-1), and (D1-1).

The measured results of the electrical insulating properties are shownin Table 15. The examples exhibited a high volume resistivity, evenafter cross-linking, and improved space charge characteristics andwater-treeing properties. By means of adding (D1-1), the electricalbreakdown field were also improved.

TABLE 9 Electrical insulating property Volume resistivity ElectricalSpace Room breakdown charge Water- temperature 90° C. field charac-treeing Example (Ωcm) (Ωcm) (MV/cm) teristics resistance 1 2.5 × 10¹⁹1.0 × 10¹⁸ 4.2 ◯ ◯ 2 1.9 × 10¹⁹ 9.0 × 10¹⁷ 4.4 ◯ ◯ 3 1.0 × 10¹⁹ 9.0 ×10¹⁷ 4.3 ◯ ◯ 4 3.0 × 10¹⁹ 2.0 × 10¹⁸ 4.2 ◯ ◯ 5 3.5 × 10¹⁹ 2.6 × 10¹⁸ 4.2◯ ◯ 6 4.0 × 10¹⁹ 2.1 × 10¹⁸ 4.2 ◯ ◯ 7 3.4 × 10¹⁹ 3.0 × 10¹⁸ 4.4 ◯ ◯ 82.1 × 10¹⁹ 1.0 × 10¹⁸ 4.1 ◯ ◯ 9 1.3 × 10¹⁹ 2.5 × 10¹⁸ 4.3 ◯ ◯ 10 1.2 ×10¹⁹ 8.0 × 10¹⁷ 4.1 ◯ ◯ 11 2.4 × 10¹⁹ 2.0 × 10¹⁸ 4.1 ◯ ◯ 12 2.7 × 10¹⁹1.1 × 10¹⁸ 4.0 ◯ ◯

TABLE 10 Electrical insulating property Volume resistivity ElectricalSpace Room breakdown charge Water- temperature 90° C. field charac-treeing Example (Ωcm) (Ωcm) (MV/cm) teristics resistance 13 1.9 × 10¹⁹2.0 × 10¹⁸ 4.3 ◯ ◯ 14 1.0 × 10¹⁹ 5.0 × 10¹⁷ 3.9 ◯ ◯ 15 2.1 × 10¹⁹ 1.1 ×10¹⁸ 4.2 ◯ ◯ 16 2.0 × 10¹⁹ 1.0 × 10¹⁸ 4.0 ◯ ◯ 17 9.9 × 10¹⁸ 7.9 × 10¹⁷4.0 ◯ ◯ 18 2.4 × 10¹⁹ 1.0 × 10¹⁸ 4.5 ◯ ◯ 19 1.6 × 10¹⁹ 1.8 × 10¹⁸ 4.4 ◯◯ 20 2.6 × 10¹⁹ 2.1 × 10¹⁸ 4.3 ◯ ◯ 21 1.2 × 10¹⁹ 3.5 × 10¹⁷ 3.9 ◯ ◯ 225.0 × 10¹⁸ 7.0 × 10¹⁷ 3.9 ◯ ◯ 23 2.4 × 10¹⁹ 4.0 × 10¹⁷ 4.0 ◯ ◯

TABLE 11 Electrical insulating property Volume resistivity ElectricalSpace Room breakdown charge Water- temperature 90° C. field charac-treeing Example (Ωcm) (Ωcm) (MV/cm) teristics resistance 24 2.7 × 10¹⁹7.0 × 10¹⁷ 4.1 ◯ ◯ 25 3.9 × 10¹⁹ 2.6 × 10¹⁸ 4.4 ◯ ◯ 26 4.0 × 10¹⁹ 3.0 ×10¹⁸ 4.5 ◯ ◯ 27 2.4 × 10¹⁹ 3.5 × 10¹⁷ 3.9 ◯ ◯ 28 1.4 × 10¹⁹ 3.9 × 10¹⁷4.0 ◯ ◯ 29 6.1 × 10¹⁸ 1.9 × 10¹⁷ 3.9 ◯ ◯ 30 9.5 × 10¹⁸ 2.5 × 10¹⁷ 4.0 ◯◯ 31 8.0 × 10¹⁸ 2.0 × 10¹⁷ 4.0 ◯ ◯ 32 1.6 × 10¹⁹ 8.5 × 10¹⁷ 4.4 ◯ ◯ 332.1 × 10¹⁹ 1.0 × 10¹⁸ 4.3 ◯ ◯

TABLE 12 Electrical insulating property Volume resistivity ElectricalSpace Room breakdown charge Water- temperature 90° C. field charac-treeing Example (Ωcm) (Ωcm) (MV/cm) teristics resistance 34 2.5 × 10¹⁸1.0 × 10¹⁷ 4.1 ◯ ◯ 35 6.0 × 10¹⁸ 4.0 × 10¹⁷ 4.1 ◯ ◯ 36 1.2 × 10¹⁸ 5.8 ×10¹⁶ 4.2 ◯ ◯ 37 1.4 × 10¹⁸ 8.5 × 10¹⁶ 4.0 ◯ ◯ 38 2.3 × 10¹⁸ 8.8 × 10¹⁶4.1 ◯ ◯ 39 1.8 × 10¹⁸ 1.0 × 10¹⁷ 4.0 ◯ ◯ 40 4.6 × 10¹⁸ 1.5 × 10¹⁷ 3.9 ◯◯ 41 1.0 × 10¹⁸ 4.9 × 10¹⁶ 3.9 ◯ ◯ 42 2.1 × 10¹⁸ 2.0 × 10¹⁷ 4.1 ◯ ◯ 431.9 × 10¹⁸ 1.3 × 10¹⁷ 4.0 ◯ ◯ 44 1.6 × 10¹⁸ 1.4 × 10¹⁷ 4.0 ◯ ◯ 45 1.1 ×10¹⁸ 5.1 × 10¹⁶ 3.8 ◯ ◯

TABLE 13 Electrical insulating property Volume resistivity ElectricalSpace Room breakdown charge Water- temperature 90° C. field charac-treeing Example (Ωcm) (Ωcm) (MV/cm) teristics resistance 46 2.0 × 10¹⁸8.6 × 10¹⁶ 4.1 ◯ ◯ 47 9.8 × 10¹⁷ 8.9 × 10¹⁶ 4.1 ◯ ◯ 48 2.5 × 10¹⁸ 1.2 ×10¹⁷ 4.1 ◯ ◯ 49 2.2 × 10¹⁸ 1.5 × 10¹⁷ 4.1 ◯ ◯ 50 1.2 × 10¹⁸ 7.2 × 10¹⁶4.1 ◯ ◯ 51 6.5 × 10¹⁸ 3.5 × 10¹⁷ 4.3 ◯ ◯ 52 6.4 × 10¹⁸ 3.4 × 10¹⁷ 4.3 ◯◯ 53 5.0 × 10¹⁸ 3.9 × 10¹⁷ 4.0 ◯ ◯ 54 5.2 × 10¹⁸ 3.0 × 10¹⁷ 4.0 ◯ ◯ 552.0 × 10¹⁸ 1.1 × 10¹⁷ 3.9 ◯ ◯ 56 2.0 × 10¹⁸ 1.3 × 10¹⁷ 4.0 ◯ ◯

TABLE 14 Electrical insulating property Volume resistivity ElectricalSpace Room breakdown charge Water- temperature 90° C. field charac-treeing Example (Ωcm) (Ωcm) (MV/cm) teristics resistance 57 2.2 × 10¹⁸1.3 × 10¹⁷ 4.0 ◯ ◯ 58 9.9 × 10¹⁷ 6.3 × 10¹⁶ 3.8 ◯ ◯ 59 5.0 × 10¹⁸ 8.5 ×10¹⁷ 4.8 ◯ ◯ 60 4.0 × 10¹⁸ 7.0 × 10¹⁷ 4.7 ◯ ◯ 61 2.0 × 10¹⁸ 2.0 × 10¹⁷4.5 ◯ ◯ 62 5.3 × 10¹⁸ 8.5 × 10¹⁷ 5.0 ◯ ◯ 63 5.5 × 10¹⁸ 9.6 × 10¹⁷ 5.0 ◯◯ 64 9.6 × 10¹⁸ 9.9 × 10¹⁷ 5.0 ◯ ◯ 65 3.2 × 10¹⁸ 1.4 × 10¹⁷ 4.8 ◯ ◯ 662.4 × 10¹⁹ 3.5 × 10¹⁷ 4.8 ◯ ◯ 67 3.4 × 10¹⁹ 3.0 × 10¹⁸ 5.0 ◯ ◯

TABLE 15 Electrical insulating property Volume resistivity ElectricalSpace Room breakdown charge Water- temperature 90° C. field charac-treeing Example (Ωcm) (Ωcm) (MV/cm) teristics resistance 68 1.5 × 10¹⁹6.4 × 10¹⁷ 4.9 ◯ ◯ 69 9.3 × 10¹⁸ 7.0 × 10¹⁷ 4.8 ◯ ◯ 70 1.6 × 10¹⁹ 7.9 ×10¹⁷ 4.9 ◯ ◯ 71 1.0 × 10¹⁹ 7.0 × 10¹⁷ 4.9 ◯ ◯ 72 3.5 × 10¹⁸ 7.0 × 10¹⁷4.9 ◯ ◯ 73 9.8 × 10¹⁸ 7.2 × 10¹⁷ 5.0 ◯ ◯ 74 3.1 × 10¹⁸ 8.0 × 10¹⁷ 4.8 ◯◯ 75 8.8 × 10¹⁸ 9.5 × 10¹⁷ 4.9 ◯ ◯ 76 1.2 × 10¹⁸ 6.8 × 10¹⁷ 4.8 ◯ ◯ 774.8 × 10¹⁸ 5.8 × 10¹⁷ 4.9 ◯ ◯ 78 1.1 × 10¹⁸ 1.0 × 10¹⁷ 4.2 ◯ ◯ 79 2.9 ×10¹⁸ 7.8 × 10¹⁷ 4.9 ◯ ◯

Comparative Example 1 to 19

The components selected from among the components (A), (C), (D) and (E)were used according to the mixing ratio shown in Tables 16 and 17, andcross-linked as necessary.

TABLE 16-1 Resin composition Component (A) Component (E) Component (C)Component (D) Parts Parts Parts Parts Comparative by by by by ExampleType weight Type weight Type weight Type weight 1 A'1 100.0 2 A'1 100.03 A'2 100.0 4 A'2 100.0 5 A'3 100.0 6 A'4 100.0 7 A'5 100.0 8 A1  100.09 A1  100.0 10 A2  100.0

TABLE 16-2 Resin composition Measurement Com- Functional Number ofcondition parative Aromatic group ethylenic Cross- Exam- componentcomponent linkages Cross- linking ple (mol/g) Type (mol/g) (per 1000 C)linking agent 1 None 2 Present DCP 3 None 4 Present PH 5 None 6 None 7None 8 None 9 Present PH 10 None

TABLE 17-1 Resin composition Component (A) Component (E) Component (C)Component (D) Parts Parts Parts Parts Comparative by by by by ExampleType weight Type weight Type weight Type weight 11 A2 100.0 12 A3 100.013 A1 10.0  A'1 90.0 14 A1 10.0  A'1 90.0 15 A2 10.0  A'1 90.0 16 A198.5 C1-1 1.5 17  A'4 92.0 C2-1 8.0 18  A'5 92.0 C2-1 8.0 19 A1 99.93D6-1 0.07

TABLE 17-2 Resin composition Measurement Com- Aromatic Number ofcondition parative com- Functional group ethylenic Cross- Exam- ponentcomponent linkages (per Cross- linking ple (mol/g) Type (mol/g) 1000 C)linking agent 11 Present PH 12 None 13 None 14 Present DCP 15 None 16 M13.8 × 10⁻⁷ None 17 M1 2.0 × 10⁻⁶ None 18 M1 2.0 × 10⁻⁶ None 19 4.8 ×10⁻⁷ M2 1.3 × 10⁻⁸ None

As Comparative Examples 1 to 7, the measured results of othernon-cross-linked and cross-linked polyolefins (A′) are shown in Table18.

Both the volume resistivity and electrical breakdown field were low, andspace charge characteristics and water-treeing properties wereunfavorable.

As Comparative Examples 8 to 12, the measured results ofnon-cross-linked, and cross-linked ethylene copolymers (A) are shown inTable 18.

Each of the aforementioned property was better than that of the abovepolyolefins (A′); however, these properties were not satisfactory.

As Comparative Examples 13 to 15, the measured results ofnon-cross-linked, and cross-linked blended products of the ethylenecopolymer (A) and the other polyolefin (A′) are shown in Table 18.

As in the case of the ethylene copolymer (A) alone, each property wasbetter than that of the other polyolefin (A′), however, these propertiesoverall were unsatisfactory.

Comparative Examples 16 and 19 are blended products of the ethylenecopolymer (A), and a graft copolymer (C11) obtained by means ofmodifying the ethylene copolymer (A) using a functional group-containingmonomer(M1); or a graft copolymer (D6) obtained by means of modifyingthe ethylene copolymer (A) using at least one monomer selected from (M1)to (M4) and an aromatic ring-containing monomer (M5). These examplescomprise compositions obtained by means of blending samples (A-1), and(C1-1) or (D6-1).

The measured results of the electrical insulating properties are shownin Table 18. Since the content of the monomer unit was 5×10⁻⁷ mol lessper one gram of the resin components, there were no improvements seen inthe volume resistivity, electrical breakdown field, or space chargecharacteristics.

Comparative Examples 17 and 18 represent compositions comprising anotherpolyolefin (A′), such as linear low density polyethylene obtained bymeans of using a single site-type catalyst or metallocene catalyst, anda graft copolymer (C21) obtained by means of modifying the otherpolyolefin (A′) using a functional group-containing monomer (M1).

The measured results of the electrical insulating properties are shownin Table 18. Since these examples did not contain the ethylene copolymer(A), none of electrical insulating properties, i.e., the volumeresistivity, electrical breakdown field, and space chargecharacteristics, were satisfactory.

TABLE 18 Electrical insulating property Volume resistivity ElectricalRoom breakdown Water- Comparative temperature 90° C. field Space chargetreeing Example (Ωcm) (Ωcm) (MV/cm) characteristics resistance 1 2.0 ×10¹⁷ 2.0 × 10¹⁵ 3.3 Large like- X polarity 2 6.0 × 10¹⁶ 6.1 × 10¹⁴ 3.1Large reverse X polarity 3 1.6 × 10¹⁸ 9.2 × 10¹⁵ 3.4 Large reverse Xpolarity 4 1.1 × 10¹⁷ 8.1 × 10¹⁴ 3.2 Large reverse X polarity 5 9.0 ×10¹⁸ 1.0 × 10¹⁸ 4.5 Large reverse Δ polarity 6 1.0 × 10¹⁸ 1.0 × 10¹⁷ 3.7Small like- Δ polarity 7 1.0 × 10¹⁸ 1.0 × 10¹⁷ 3.7 Small like- Δpolarity 8 3.5 × 10¹⁸ 5.6 × 10¹⁷ 3.9 Large like- ◯ polarity 9 5.0 × 10¹⁷5.0 × 10¹⁶ 3.8 Large like- ◯ polarity 10 2.6 × 10¹⁸ 4.1 × 10¹⁷ 4.2 Largelike- ◯ polarity 11 3.5 × 10¹⁷ 4.8 × 10¹⁶ 4.1 Large like- ◯ polarity 124.0 × 10¹⁸ 6.0 × 10¹⁷ 4.0 Large like- ◯ polarity 13 2.3 × 10¹⁸ 8.0 ×10¹⁶ 3.7 Large like- Δ polarity 14 4.0 × 10¹⁷ 2.5 × 10¹⁵ 3.6 Largereverse Δ polarity 15 1.9 × 10¹⁸ 7.0 × 10¹⁶ 4.0 Large like- Δ polarity16 4.0 × 10¹⁸ 6.0 × 10¹⁷ 3.8 Small like- Δ polarity 17 5.1 × 10¹⁸ 2.3 ×10¹⁷ 3.7 Small like- Δ polarity 18 4.5 × 10¹⁸ 1.7 × 10¹⁵ 3.9 Smallreverse Δ polarity 19 2.9 × 10¹⁸ 6.2 × 10¹⁷ 3.8 Large reverse Δ polarity

(Electric Wire Covering Properties)

Copper wires were respectively covered by the compositions of Examples4, 10, 34, 51, and 62, and their processabilities were evaluated. Thecovering conditions were as follows: core wire of 0.9 mm; dice diameterof 2.5 mm; nipple diameter of 0.95 mm; dice nipple clearance of 5.3 mm;finished outer diameter of 2.45 mm; and winding speed of 100 m/minute.After covering, upon visual examination, the surface roughness of theexamples was small, such that the example were deemed appropriate forpractical use.

(Manufacturing of Cables)

Using the compositions of Examples 4, 10, 34, 51, and 62, the cablesshown in FIG. 5 were manufactured. Both the manufacturability andproperties of the cable were favorable.

The electric cable shown in FIG. 5 formed a concentric circlecomprising, from the innermost to outermost material, a conductormaterial 21 comprising aggregated wires of conductive metal; innersemiconductor layer 22; insulating layer 23 comprising the ethylenecopolymer; outer semiconductor layer 24; aluminum foil 25; andprotective material 26 (inorganic flame retardant-containingpolyolefin).

Industrial Applicability

The resin material for an electrical insulating material according tothe present invention contains ethylenic linkages and/or a specificmonomer unit in the resin component therein, which contains an ethyleneα-olefin copolymer (A) which satisfies the aforementioned specificconditions. Accordingly, the resin material for an electrical insulatingmaterial according to the present invention exhibits a superiorprocessability and thermal resistance, in addition to superiorelectrical insulating properties, such as superior volume resistivity,space charge characteristics, dielectric breakdown strength,water-treeing resistance, and the like, in which a reduction in themechanical strength does not occur. In addition, the resin material foran electrical insulating materials according to the present invention isrich in cross-linkability, and even after cross-linking, exhibitssuperior volume resistivity, space charge characteristics, dielectricbreakdown strength, water-treeing resistance, and the like.

Furthermore, when the halogen concentration in the aforementionedcopolymer of ethylene and C₄₋₁₂ α-olefin is 10 ppm or less, it becomesunnecessary to supply additives such as a halogen acceptor, and thelike, which in turn leads to superior electrical insulating properties.

In addition, when the aforementioned copolymer of ethylene and C₄₋₁₂α-olefin is obtained by means of copolymerizing ethylene and C₄₋₁₂α-olefin in the presence of a catalyst comprising an cyclic organiccompound containing at least a conjugated double bond, and a compoundcontaining transition metal from group IV of the Periodic Table, itsprocessability, thermal resistance, mechanical strength, and electricalinsulating performance are further improved.

In addition, the electrical insulating material according to the presentinvention employs one of the aforementioned resin materials for anelectrical insulating material, and thus exhibits a superiorprocessability, thermal resistance, mechanical strength, and electricalinsulating properties.

Furthermore, when one of the aforementioned resin materials for anelectrical insulating material is first cross-linked and then used, themechanical strength is further improved.

The resin material for an electrical insulating material and electricalinsulating material formed in this manner may be used as a electric wireand cable, insulating material for a condenser, and as an insulatingmaterial and distributing cord for high electrical voltage parts such asan X-ray generator, or the like.

In addition, the electric wire and cable according to the presentinvention employs the aforementioned non-cross-linked or cross-linkedelectrical insulating material, and thus exhibits a superior mechanicalstrength and electrical insulating properties.

What is claimed is:
 1. An electrical insulating material comprising aresin material for an electrical insulating material comprising a resincomponent which comprises an ethylene α-olefin copolymer (A), obtainedby means of copolymerizing ethylene and C₄₋₁₂ α-olefin, said ethyleneα-olefin copolymer (A) satisfying specific conditions (i) to (v): (i) adensity d of 0.92 to 0.96 g/cm³, (ii) a melt flow rate (MFR) of 0.01 to200 g/10 minutes, (iii) a molecular weight distribution (Mw/Mn) of 1.5to 5.0, (iv) possessing only one peak in terms of the number of peaksobserved in an elution temperature-eluted amount curve as measured bythe continuous temperature raising elution fractionation (TREF) method,and from the integrated elution curve obtained by said elutiontemperature-eluted amount curve, the difference T₇₅−T₂₅ in thetemperature and said density d respectively follow the relationshipsshown by formula a and formula b, wherein T₂₅ is the temperature where25% of the total elution is obtained, and T₇₅ is the temperature where75% of the total elution is obtained; and (v) possessing one or twomelting point peaks, and among these the highest melting point T_(m) andsaid density d follow the relationship described by formula c; whereinsaid resin component contains a unit (B) derived from at least one typeof monomer selected from the group consisting of a carbonyl or carbonylderivative group-containing monomer (M1), a hydroxyl group-containingmonomer (M2), a nitro group-containing monomer (M3), a nitrilegroup-containing monomer (M4), an aromatic ring-containing monomer (M5)and a compound or monomer containing two or more ethylenic linkages(M6); and when said unit (B) is derived from at least one type ofmonomer selected from M1 to M5, the concentration of said unit (B)ranges from 5×10⁻⁷ to 5×10⁻³ mol per one gram of said resin component,and when said unit (B) is derived from M6, the number of ethyleniclinkages per 1000 carbon atoms of said resin component is at least 0.8,if d<0.950 g/cm³, then  (Formula a) T ₇₅ −T ₂₅≧−300×d+285 if d≧0.950g/cm³, then T ₇₅ −T ₂₅≧0 T ₇₅ −T ₂₅≦−670×d+644  (Formula b) T_(m1)≧150×d−17  (Formula c)
 2. An electrical insulating materialaccording to claim 1, comprising a maleic anhydride-modified ethyleneα-olefin copolymer (A).
 3. An electrical insulating material accordingto claim 1, comprising a maleic anhydride-modified ethylene α-olefincopolymer (A) and an ethylene-styrene random copolymer.
 4. An electricalinsulating material comprising a cross-linked resin material obtained bycross-linking of a resin material for an electrical insulating materialaccording to claim
 1. 5. An electrical insulating material according toclaim 4, wherein a resin material for an electrical insulating materialcomprising a maleic anhydride-modified liquid polybutadiene, and amaleic anhydride-modified ethylene α-olefin copolymer (A) iscross-linked.
 6. An electrical insulating material according to claim 4,wherein a resin material for an electrical insulating materialcomprising a maleic anhydride-modified liquid polybutadiene, and anethylene-styrene random copolymer is cross-linked.
 7. An electricalinsulating material according to claim 4, wherein a resin material foran electrical insulating material comprising a maleic anhydride-modifiedliquid polybutadiene, maleic anhydride-modified ethylene α-olefincopolymer (A) and an ethylene-styrene random copolymer is cross-linked.8. An electrical insulating material according to claim 1, wherein saidethylene α-olefin copolymer (A) satisfies specific conditions (i) to(vii): (i) a density d of 0.92 to 0.96 g/cm³, (ii) a melt flow rate(MFR) of 0.01 to 200 g/10 minutes, (iii) a molecular weight distribution(Mw/Mn) of 1.5 to 3.5, (iv) possessing only one peak in terms of thenumber of peaks observed in an elution temperature-eluted amount curveas measured by the continuous temperature raising elution fractionation(TREF) method, and from the integrated elution curve obtained by saidelution temperature-eluted amount curve, the difference T₇₅−T₂₅ in thetemperature and said density d respectively follow the relationshipsshown by formula a and formula b, wherein T₂₅ is the temperature where25% of the total elution is obtained, and T₇₅ is the temperature where75% of the total elution is obtained; (v) possessing one or two meltingpoint peaks, and among these the highest melting,point T_(m1) and saiddensity d follow the relationship described by formula c; (vi) anelectrical activation energy of no greater than 0.4 eV; and (vii) themelt tension (MT) and melt flow rate (MFR) follow the relationship shownby formula d; if d<0.950 g/cm³, then  (Formula a) T ₇₅ −T ₂₅≧−300×d+285if d≧0.950 g/cm³, then T ₇₅ −T ₂₅≧0 T₇₅ −T ₂₅≦−670×d+644  (Formula b) T_(m1)≧150×d−17  (Formula c) log MT≦−0.572×log MFR+0.3.  (Formula d) 9.An electrical insulating material according to claim 1, wherein saidethylene α-olefin copolymer (A) is obtained by means of copolymerizingethylene and a C₄₋₁₂ α-olefin under the presence of a catalystcomprising a cyclic organic compound containing at least a conjugateddouble bond, and a compound containing transition metal from group IV ofthe Periodic Table.
 10. An electrical insulating material according toclaim 1, wherein the halogen concentration within said ethylene α-olefincopolymer (A) is no greater than 10 ppm.
 11. An electrical insulatingmaterial according to claim 1, wherein said resin component comprisessaid ethylene α-olefin copolymer (A), and another polyolefin (A′). 12.An electrical insulating material according to claim 11, wherein saidother polyolefin (A′) is at least one compound selected from the groupconsisting of a polyethylene obtained by means of a high pressureradical polymerization, a high density polyethylene, a medium densitypolyethylene, and a linear low density polyethylene.
 13. An electricalinsulating material according to claim 1, wherein said carbonyl orcarbonyl derivative group-containing monomer (M1) to be introduced intosaid resin component is at least one compound selected from the groupconsisting of maleic anhydride and (meth)acrylic acid.
 14. An electricalinsulating material according to claim 13, wherein a maleicanhydride-modified ethylene α-olefin copolymer (A) is used at the timesaid carbonyl or carbonyl derivative group-containing monomer (M1) isintroduced into said resin component.
 15. An electrical insulatingmaterial according to claim 1, wherein a polystyrene, ethylene-styrenerandom copolymer, or an ethylene copolymer (A), which has been modifiedby means of grafting an aromatic ring-containing monomer, is used at thetime said aromatic ring-containing monomer (M5) is introduced into saidresin component.
 16. An electrical insulating material according toclaim 1, wherein at least one compound selected from the groupconsisting of a liquid polybutadiene, a maleic anhydride-modified liquidpolybutadiene, an ethylene-aryl(meth)acrylate copolymer, and anethylene-vinyl(meth)acrylate copolymer is used at the time said compoundor monomer containing two or more ethylenic linkages (M6) is introducedinto said resin component.
 17. An electrical insulating materialaccording to claim 1, wherein said resin component contains saidcompound or monomer containing two or more ethylenic linkages (M6) andsaid carbonyl or carbonyl derivative group-containing monomer (M1). 18.An electrical insulating material according to claim 1, wherein a maleicanhydride-modified liquid polybutadiene and a maleic anhydride-modifiedethylene α-olefin copolymer (A) are used at the time said carbonyl orcarbonyl derivative group-containing monomer (M1) and said compound ormonomer containing two or more ethylenic linkages (M6) are introducedinto said resin component.
 19. An electrical insulating materialaccording to claim 1, wherein said resin component contains saidcompound or monomer containing two or more ethylenic linkages (M6) andsaid aromatic ring-containing monomer (M5).
 20. An electrical insulatingmaterial according to claim 19, wherein a maleic anhydride-modifiedliquid polybutadiene and an ethylene-styrene random copolymer are usedat the time said compound or monomer containing two or more ethyleniclinkages (M6) and said aromatic ring-containing monomer (M5) areintroduced into said resin component.
 21. An electrical insulatingmaterial according to claim 1, wherein said resin component containssaid carbonyl or carbonyl derivative group-containing monomer (M1) andsaid aromatic ring-containing monomer (M5).
 22. An electrical insulatingmaterial according to claim 21, wherein a maleic anhydride-modifiedethylene α-olefin copolymer (A) and an ethylene-styrene random copolymerare used at the time said carbonyl or carbonyl derivativegroup-containing monomer (M1) and said aromatic ring-containing monomer(M5) are introduced into said resin component.
 23. An electricalinsulating material according to claim 1, wherein said resin componentcontains said carbonyl or carbonyl derivative group-containing monomer(M1), said compound or monomer containing two or more ethylenic linkages(M6), and said aromatic ring-containing monomer (M5).
 24. An electricalinsulating material according to claim 23, wherein a maleicanhydride-modified liquid polybutadiene, a maleic anhydride-modifiedethylene α-olefin copolymer (A) and a ethylene-styrene random copolymerare used at the time said carbonyl or carbonyl derivativegroup-containing monomer (M1), said compound or monomer containing twoor more ethylenic linkages (M6), and said aromatic ring-containingmonomer M5 are introduced into said resin component.